A020183 - OEIS

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A020183

Pseudoprimes to base 55.

6, 9, 18, 21, 27, 54, 63, 91, 153, 189, 357, 369, 553, 697, 801, 1027, 1266, 1387, 1513, 1729, 1869, 2701, 2821, 3213, 3649, 4033, 4431, 6273, 6533, 6541, 6601, 6643, 7189, 7957, 8911, 9773, 9937, 10649, 10761, 13333, 13617, 13833, 14981, 15457, 15841

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OFFSET

1,1

COMMENTS

Composite numbers n such that 55^(n-1) == 1 (mod n).

LINKS

T. D. Noe, Table of n, a(n) for n = 1..1000

Index entries for sequences related to pseudoprimes

MATHEMATICA

base = 55; t = {}; n = 1; While[Length[t] < 100, n++; If[! PrimeQ[n] && PowerMod[base, n-1, n] == 1, AppendTo[t, n]]]; t (* T. D. Noe, Feb 21 2012 *)

Select[Range[16000], CompositeQ[#]&&PowerMod[55, #-1, #]==1&] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Oct 26 2018 *)

CROSSREFS