1,1

Sequence contains primes of the form 6x+1 (A002476) and multiples of those primes, except (6x+1)^2. If x is not in the sequence, the smallest k dividing sigma(k*x^2) is equal to 6.

Table of n, a(n) for n=1..60.

(PARI) isok(n) = A049605(n^2) != 6; \\ Michel Marcus, Nov 21 2013

Cf. A049605.

Sequence in context: A233593 A013651 A050931 * A232437 A275201 A274558

Adjacent sequences: A072861 A072862 A072863 * A072865 A072866 A072867

easy,nonn

Benoit Cloitre, Jul 27 2002

approved