A237266 The n-th base 2 pseudoprime is also a pseudoprime to base 2 through base prime(a(n)).

1, 1, 1, 2, 1, 3, 1, 1, 2, 2, 3, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 3, 1, 2, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 2, 1, 1, 1, 1, 5, 1, 1, 1, 1, 2, 1, 1, 1, 1, 3, 1, 1, 5, 2, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 4, 1, 2, 2, 1, 1, 1, 2, 2, 1, 2, 3, 2, 2, 1, 5, 1, 1, 3, 1

Offset

1,4

Comments

Pseudoprime A001567(n) is a pseudoprime to base 2 through base prime(a(n)), where a(n) is this sequence.

Links

Lei Zhou, Table of n, a(n) for n = 1..10000

Example

n=1, A001567[1]=341. 341 is base 2 pseudoprime but not base 3 pesudoprime.  Since Prime(1)=2, a(1)=1;
...
n=6, A001567[1]=1729. 1729 is base 2, 3, 5 pseudoprimes but not base 7 pesudoprime.  Since Prime(3)=5, a(6)=5.

Mathematica

p = 1; fi = {}; While[Length[fi] < 87, p = p + 2; If[! PrimeQ[p], ct = 0; q = 2; While[c = q^(p - 1); Mod[c, p] == 1, q = NextPrime[q]]; If[q > 2, q = PrimePi[NextPrime[q, -1]]; AppendTo[fi, q]]]]; Print[fi]

Crossrefs

Cf. A001567, A083876, A002997.

Sequence in context: A351092 A138618 A140583 * A123507 A188804 A122580

Adjacent sequences: A237263 A237264 A237265 * A237267 A237268 A237269

Keyword

nonn

Author

Lei Zhou, Feb 05 2014

Status

approved