A015938 Smallest k>2^n such that 2^k == 2^n (mod k).

3, 6, 9, 20, 56, 66, 133, 260, 513, 1030, 2091, 4128, 8593, 16394, 33195, 65584, 131345, 262176, 524989, 1048660, 2097291, 4195642, 8388997, 16777272, 33554525, 67109198, 134217729, 268435468, 536875753, 1073741910

Offset

1,1

Links

Table of n, a(n) for n=1..30.

Example

For n=3, 2^3=8, and k=9 works, since 2^9 = 512 == 8 (mod 9).

Mathematica

f[n_] := Block[{k = 2^n + 1}, While[ PowerMod[2, k, k] != PowerMod[2, n, k], k++]; k]; Array[f, 30] (* Robert G. Wilson v, Aug 01 2011 *)

Crossrefs

Cf. A015939.

Sequence in context: A223504 A322949 A285215 * A116614 A089001 A215666

Adjacent sequences: A015935 A015936 A015937 * A015939 A015940 A015941

Keyword

nonn

Author

Robert G. Wilson v

Extensions

Constraint on k added to the definition by R. J. Mathar, Aug 01 2011

Status

approved