A217468 - OEIS

A217468

Composite values of n such that 2^n == 2 (mod n*(n-1)).

91625794219, 8796093022207, 1557609722332488343, 18216643597893471403

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OFFSET

1,1

COMMENTS

No other terms below 2^64.

The next term is <= 25790417485109157029391019 = A019320(258). - Emmanuel Vantieghem, Dec 01 2014

Terms A019320(k) belongs to this sequence for k in A297412. - Max Alekseyev, Dec 29 2017

LINKS

EXAMPLE

a(1) = 91625794219 = (2^38 - 2^19 + 1)/3 = A019320(114).

a(2) = 8796093022207 = 2^43 - 1 = A019320(43).

PROG

(PARI) is_A217468(n)={Mod(2, (n-1)*n)^n==2 & !isprime(n)} \\ - M. F. Hasler, Oct 07 2012

CROSSREFS

Intersection of A001567 and { 2*A014945(k) + 1 }.

KEYWORD

nonn,hard,more

AUTHOR

V. Raman, Oct 04 2012

STATUS

approved