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A015938 Smallest k>2^n such that 2^k == 2^n (mod k). 1
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 (list; graph; refs; listen; history; text; internal format)
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: A018186 A223504 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

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Last modified November 20 00:42 EST 2017. Contains 294957 sequences.