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

Author

Lei Zhou, Feb 05 2014

Keywords

• nonn

Comments

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

Examples

			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.
		

Links

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

Crossrefs

Cf. A001567, A083876, A002997.

Programs

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]