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A263239
Euler pseudoprimes to base 9: composite integers such that abs(9^((n - 1)/2)) == 1 mod n.
1
4, 28, 91, 121, 286, 532, 671, 703, 949, 1036, 1105, 1541, 1729, 1891, 2465, 2665, 2701, 2821, 3281, 3367, 3751, 4636, 4961, 5551, 6364, 6601, 7381, 8401, 8911, 10585, 11011, 11476, 12403, 14383, 15203, 15457, 15841, 16471, 16531, 18721, 19345, 19684, 23521, 24046, 24661, 24727
OFFSET
1,1
COMMENTS
Even numbers are permitted since 9 is an integer square. - Charles R Greathouse IV, Oct 12 2015
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..116 from Daniel Lignon)
MATHEMATICA
eulerPseudo9Q[n_]:=(Mod[9^((n-1)/2)+1, n]==0 ||Mod[9^((n-1)/2)-1, n]==0) && Not[PrimeQ[n]];
Select[Range[2, 200000], eulerPseudo9Q]
PROG
(PARI) is(n) = abs(centerlift(Mod(3, n)^(n-1)))==1 && !isprime(n) && n>1 \\ Charles R Greathouse IV, Oct 12 2015
CROSSREFS
Cf. A020138 (pseudoprimes to base 9).
Cf. A006970 (base 2), A262051 (base 3), A262052 (base 5), A262053 (base 6), A262054 (base 7), A262055 (base 8).
Sequence in context: A183485 A183437 A294315 * A296015 A187452 A173296
KEYWORD
nonn
AUTHOR
Daniel Lignon, Oct 12 2015
STATUS
approved