A256566 a(n) is the central term of the (2n-1)-st row of triangle A256440.

1, 3, 3, 3, 9, 9, 9, 2, 2, 2, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 38, 46, 46, 46, 46, 46, 46, 58, 58, 58, 58, 58, 58, 58, 58, 58, 58, 58, 58, 62, 62, 74, 74, 74, 74, 82, 82, 74, 74, 74, 62, 74, 74, 74, 74, 74, 62, 74, 74, 82, 82, 82, 82, 82, 82, 82

Offset: 1

Author

Michel Marcus, Apr 02 2015

Keywords

• nonn

Comments

All terms are deficient and after the 4th term sigma(n)/n appears to stay between 1.5 and 1.6.

Note that sequence is not monotonic and can return later to previous terms values.

Links

• Michel Marcus, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A005100 (deficient numbers), A256440.

Programs

PARI

lista(nn) = {forstep(n=1, nn, 2, v = vector(n, k, sigma(k)/k); w = vecsort(v,,1); print1(w[(n+1)/2], ", "););}