A090083 - OEIS

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A090083

Even pseudoprimes to base 9.

4, 8, 28, 52, 286, 364, 532, 616, 946, 1036, 1288, 2806, 2926, 3052, 4376, 4636, 5356, 6364, 8744, 8866, 11476, 12124, 15964, 17446, 19096, 19684, 21196, 21736, 24046, 24388, 26596, 31876

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OFFSET

1,1

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from Charles R Greathouse IV)

Index entries for sequences related to pseudoprimes.

MATHEMATICA

Do[s=Mod[ -1+9^(n-1), n]; If[Equal[s, 0]&&!PrimeQ[n]&&EvenQ[n], Print[n]], {n, 1, 1000000}]

PROG

(PARI) is(n)=Mod(9, n)^(n-1)==1&&!isprime(n)&&n%2==0 \\ Charles R Greathouse IV, Apr 12 2012

(PARI) p=2; forprime(q=3, 1e8, forstep(n=p+1, q-1, 2, if(Mod(9, n)^(n-1)==1, print1(n", "))); p=q) \\ Charles R Greathouse IV, Apr 12 2012

CROSSREFS

Cf. A020138.

Cf. A006935, A130433, A090082, A090084, A090085, A130434, A130435, A130436, A130438, A130439, A130440, A130441, A130442, A130443.

Sequence in context: A117864 A020138 A306448 * A034515 A189546 A059480

Adjacent sequences: A090080 A090081 A090082 * A090084 A090085 A090086

KEYWORD

nonn

AUTHOR

Labos Elemer, Nov 25 2003

STATUS

approved