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Show HN: mod((prime*prime-1)/12)

2 points·zipotm··7 comments

Looks like every prime number multiplied by himself minus 1 is exactly divisible by 12. Figured out that few months ago.

(Except for the prime numbers 2 and 3, of course.)

11 x 10

23×22=506 506÷12=42.16666...

Nope.

This is why mathematical statements need proofs.

(23x23-1)/12 = 44.

(11x11-1)/12 = 10.

Ah you mean (p×(p–1))÷12=(p²–p)÷12.

In that case it’s just the old p=6n±1.

elegant

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