1,1

Terms are the indices of zeros in A125162, i.e. A125162[a(n)] = 0.

Table of n, a(n) for n=1..72.

A125162 begins {1,1,1,1,3,1,4,0,1,1,5,1,3,0,1,1,6,1,7,0,1,1,6,0,1,0,1,1,6,1,9,0,0,0,3,1,11,0,1,1,9,1,5,0,1,1,10,0,2,0,1,1,9,0,2,0,1,1,10,1,9,0,0,0,3,1,9,0,1,1,8,1,9,0,0,0,5,1,9,0,1,1,11,0,1,0,1,1,8,0,3,0,0,0,2,1,10,0,1,1,...}.

Thus a(1) = 8, a(2) = 14, a(3) = 20, a(4) = 24, a(5) = 26, a(6)-a(8) = {32,33,34}.

(PARI) b(n)=c=0; for(k=1, n, if(ispseudoprime(k!+n), c++)); c

n=1; while(n<500, if(!b(n), print1(n, ", ")); n++) \\ Derek Orr, Oct 15 2014

Cf. A125162 = number of primes of the form k! + n. Cf. A125164 = numbers n such that no prime exists of the form (k! + 3n - 1), (k! + 3n), (k! + 3n + 1).

Sequence in context: A068638 A025044 A264722 * A309355 A063288 A136798

Adjacent sequences: A125160 A125161 A125162 * A125164 A125165 A125166

nonn

Alexander Adamchuk, Nov 21 2006

More terms from Derek Orr, Oct 15 2014

Edited by Michel Marcus, Jul 29 2018

approved