A115976 - OEIS

A115976

Numbers k that divide 2^(k-2) + 1.

1, 3, 49737, 717027, 9723611, 21335267, 32390921, 38999627, 43091897, 86071337, 101848553, 102361457, 228911411, 302948067, 370219467, 393664027, 455781089, 483464027, 1040406177, 1272206987, 2371678553, 2571052241, 2648052857, 3054713937, 3597613307, 3782971499, 3917903851, 4005163577, 5419912241

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OFFSET

1,2

COMMENTS

Some larger terms: 4465786944074559659, 1440261542571735083956640176981881665928575750093930787551969

LINKS

Max Alekseyev, Table of n, a(n) for n = 1..708 (contains all terms below 10^15)

MATHEMATICA

lst = {}; Do[ If[ PowerMod[2, 2n - 3, 2n - 1] == 2n - 2, AppendTo[lst, 2n - 1]], {n, 10^9}]; lst (* Robert G. Wilson v, Apr 04 2006 *)

CROSSREFS

The odd elements of A244673.