A072864 Numbers n such that the smallest k dividing sigma(k*n^2) is equal to 3.

7, 13, 14, 19, 21, 26, 28, 31, 35, 37, 38, 39, 42, 43, 52, 56, 57, 61, 62, 63, 65, 67, 70, 73, 74, 76, 77, 78, 79, 84, 86, 91, 93, 95, 97, 103, 104, 105, 109, 111, 112, 114, 117, 119, 122, 124, 126, 127, 129, 130, 133, 134, 139, 140, 143, 146, 148, 151, 152, 154

Offset

1,1

Comments

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.

Links

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

Prog

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

Crossrefs

Cf. A049605.

Sequence in context: A013651 A379301 A050931 * A232437 A275201 A274558

Adjacent sequences: A072861 A072862 A072863 * A072865 A072866 A072867

Keyword

easy,nonn

Author

Benoit Cloitre, Jul 27 2002

Status

approved