A331033 a(n) is the least k such that the denominator(sigma(sigma(k))/k) equals n.

1, 30, 3, 32, 5, 864, 7, 128, 9, 10, 11, 96, 13, 3570, 45, 256, 17, 216, 19, 40, 147, 22, 23, 6912, 25, 468, 567, 224, 29, 2520, 31, 416, 33, 374, 35, 147456, 37, 152, 117, 10800, 41, 102816, 43, 88, 135, 46, 47, 768, 49, 21000, 153, 52, 53, 6696, 165, 896, 171, 7424, 59, 36960

Offset

1,2

Comments

a(n) is the least k such that the A318060(k) equals n.

a(n) is divisible by n.

Links

Ray Chandler, Table of n, a(n) for n = 1..10000

Prog

(PARI) a(n) = my(k=n); while (denominator(sigma(sigma(k))/k) != n, k+=n); k;

Crossrefs

Cf. A000203 (sigma), A051027 (sigma(sigma)), A318060.

Cf. A019278, A330598, A331019.

Sequence in context: A040885 A040887 A040888 * A040889 A307026 A040882

Adjacent sequences: A331030 A331031 A331032 * A331034 A331035 A331036

Keyword

nonn

Author

Michel Marcus, Jan 08 2020

Status

approved