Why buy a card for one specific year when you can buy the same birthday card but generalised! This card works seamlessly for any integer age your friend/colleague/you may be turning. You could even argue* the case that n does not strictly have to be an integer, in which case you could literally give this card to any person on any day of the year. Now that's a versatile birthday card.

Inside the card it says "You look exactly a day over n-1" because we're all about honesty here at Maths Gear.

Also available in a set of five identical cards. Give them to five different people, or just the same person year after year after year...

As seen in Matt Parker's stand-up show Humble Pi.

*best to write out said argument inside the card before you give it away.

Single card (with envelope) £4.00

Pack of 5 (with envelopes) £10.00