Here is the simple formula:

The shill multiplies the card value by 4 and then subtracts 1. That's it!

Because this is part of the LAZY series this means the magician will equivoque to force a red card selection (Diamonds or Hearts).

The magician uses a 51 card deck. The normal last card (in position 52) is a black card and it is removed before the performance and not used.

So how can the same formula work for both Diamonds (ascending) and Hearts (descending)?

Simple, If a Diamond was said by the spectator then the magician deals from the top of the deck counting 1, 2, 3, 4, 5 etc.

If a Heart was said by the spectator then the magician turns the deck face up and deals from what was the bottom of the deck counting 1, 2, 3, 4, 5 etc.

Below is the physical deck (note this is the same as B3 and B4 but the formula and method for B5 has been simplified).

Lazy-B5 physical stack:
KH, 3S, AD, 7C, QH, KC, 2D, 8S, JH, 5S, 3D, 6C, 10H, KS, 4D, 2S, 9H, 6S, 5D, 10C, 8H, QC, 6D, 3C, 7H, AC, 7D, 9C, 6H, 10S, 8D, 4C, 5H, JS, 9D, 7S, 4H, 2C, 10D, 4S, 3H, AS, JD, 9S, 2H, QS, QD, 8C, AH, JC, KD
Note that the above is a 51 card deck (the last card which in this case is the 5C has been permanently removed).

Lazy-B5
Card to number:
Magician says "imagine a deck of cards, do you want me to pull out the red cards or the black cards"? Regardless of their answer you proceed with the red cards asking which suit Hearts or Diamonds and then asking whether they want a picture card or number card and then asking them to name the specific card.

The card is named by the spectator therefore the below calculation is done by the shill so he can say the position of that card (and that position will always be an odd number because the red cards are all at odd number positions counting from the face down top of the deck or countng from the face up bottom of the deck and the formula below for "card to number" will give the correct odd number).

After the spectator names a red card the shill mentally does the below calculation and names the card position number.

Whether Hearts or Diamonds makes no difference to the shill because he just:

Card to number:
1. multiplies the card value by four and then subtracts one.
2. verbally says the number.

Number to Card (spectator says a number from one to 52).
Note that when doing "Number to card" the Shill calculates:
1 . divide the spectator's number by 4.
2. the REMAINDER will indicate THE SUIT ie: 1 means Hearts, 3 means Diamonds.
3. If the number named by the spectator is an odd number then add one to the QUOTIENT.
4. the shill says the QUOTIENT (which is the card value) and then says the suit name based on the remainder in step two above.

Important note when doing "number to card":
It is best if the magician also divides by four to know the remainder so he can turn the deck face up IF THE REMAINDER IS 1 (I think it looks better if the magician turns the deck face up (when Hearts) before the shill names the card but it is okay if the magician waits to hear the shill say the suit "Hearts" and then turn the deck face up).

Another very important note when doing "number to card": If the spectator says an EVEN NUMBER then the magician (while holding the deck face down if Diamonds and holding the deck face up if Hearts) must cut a single card from the bottom of the stack he is holding to the top. I like to do a pinky pull down of the bottom card and then just do a double undercut.

If you are not comfortable with doing the double undercut (when doing number to card and the spectator says an even number) then you can blatantly take the bottom card, It will be a king, and claim it has magical powers and wave it at the deck and then casually put it on top.

Some magicians may feel that the spectator is more likely to say a Heart than a Diamond, in that case then it would be better to make Diamonds the face up count instead of Hearts.

To make this perminent change: holding the deck face down just deal the above 51 card stack face down onto a single pile as this will reverse the entire stack and make hearts the dominant face down counting suit (you also have to change the instructions above that everywhere that it says "Hearts" to do it for "Diamonds" instead).

Note: originally I had a black card on top and an extra black card on the bottom giving a 53 card deck and the reason for this was to eliminate the "minus one" portion of the calculation so that the calculation would simply be "the card value times 4".

But thinking it over I thought that might be a little too obvious to the spectators to see exact multiples of four being stated by the shill therefore I decided to use the minus 1 calculation and thus the 51 card deck with a red king on the top and bottom.

Correction: when doing "number to card" my instructions say "If the remainder is 1" however the spectator may have said an even number therefore those instructions should say "If the remainder is 1 or 2". Also any instructions that say "remainder of three" should say "If remainder is 3 or 0".

There is a bug in the "number to card" formula.
Note that the "card to number" formula is perfect however the "NUMBER TO CARD" DOES NOT work if the following numbers were said by the spectator: 1, 2, 5, 6, 9, 10, 13, 14, 17, 18, 21, 22, 25, 26, 29, 30, 33, 34, 37, 38, 41, 42, 45, 46, 49, 50. which is saying that if the remainder is one or two (hearts) the formula for number to card does not work.

The "number to card" formula DOES work
for the following numbers said by the spectator 3, 4, 7, 8, 11, 12, 15, 16, 19, 20 23, 24 27, 28, 31, 32, 35, 36, 39, 40, 43, 44, 47, 48, 51, 52 Note that these will all hit the ascending suit (diamonds). Also reminder that if an even number is said the magician will move one card from the bottom of the stack he is holding to the top, but this does not help the descending suit (Hearts) for the "number to card" calculation.

For the descending suit (hearts ie: remainder 1 or 2) the calculation (for "number to card") after dividing by 4 should be 13 minus the quotient.