

A066488


Composite numbers n which divide A001045(n1).


2



341, 1105, 1387, 1729, 2047, 2465, 2701, 2821, 3277, 4033, 4369, 4681, 5461, 6601, 7957, 8321, 8911, 10261, 10585, 11305, 13741, 13747, 13981, 14491, 15709, 15841, 16705, 18721, 19951, 23377, 29341, 30121, 30889, 31417, 31609, 31621, 34945
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OFFSET

1,1


COMMENTS

Also composite numbers n such that ((2^n  2)/3 + 1) == 2^n 1 == 1 (mod n).
An equivalent definition of this sequence: pseudoprimes to base 2 that are not divisible by 3.  Arkadiusz Wesolowski, Nov 15 2011


LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000


MATHEMATICA

a[0] = 0; a[1] = 1; a[n_] := a[n] = a[n  1] + 2a[n  2]; Select[ Range[50000], IntegerQ[a[ #  1]/ # ] && !PrimeQ[ # ] && # != 1 & ]
fQ[n_] := ! PrimeQ@ n && Mod[((2^n  2)/3 + 1), n] == Mod[2^n  1, n] == 1; Select[ Range@ 35000, fQ]


PROG

(PARI) is(n)=n%3 && Mod(2, n)^(n1)==1 && !isprime(n) && n>1 \\ Charles R Greathouse IV, Sep 18 2013


CROSSREFS

Cf. A066047.
Sequence in context: A172255 A087835 A271221 * A291601 A083876 A068216
Adjacent sequences: A066485 A066486 A066487 * A066489 A066490 A066491


KEYWORD

easy,nonn


AUTHOR

Robert G. Wilson v, Jan 03 2002


STATUS

approved



