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

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.

Cf. A006521, A006517, A069927, A067945, A067946, A067947, A068382, A068383, A014945, A014946, A014949, A092028.

Sequence in context: A086829 A190722 A171365 * A340182 A367550 A178966

Adjacent sequences: A115973 A115974 A115975 * A115977 A115978 A115979

Keyword

nonn

Author

Max Alekseyev, Mar 15 2006

Extensions

More terms from Robert G. Wilson v, Apr 04 2006

Terms a(24) onward from Max Alekseyev, Feb 03 2015

b-file corrected and extended by Max Alekseyev, Oct 27 2018

Status

approved