A349007 a(1) = 1; for n > 1, a(n) is the largest number m such that sigma(m) = tau(m)^n or 0 if no such m exists.

1, 3, 7, 2667, 27559, 677207307, 225735769, 698915267211, 29587412978599, 811637999283747, 16907189874529, 12200855315219510767697163, 254155396405925065290841, 878412242330556407427, 1074593611687774330088252281, 16138807601873739769, 37471768236581557067194399

Offset

1,2

Comments

See A051281 for numbers m such that sigma(m) = tau(m)^k where k = integer.

a(n) = 0 for n = 76, 81, ...

Links

Table of n, a(n) for n=1..17.

Rémy Sigrist, PARI program for A349007

Example

a(4) = 2667 because 2667 is the largest number m such that sigma(m) = tau(m)^4; sigma(2667) = 4096 = tau(2667)^4  = 8^4.

Prog

(PARI) See Links section.

Crossrefs

Subsequence of A051281.

Cf. A000005 (tau), A000203 (sigma), A334455, A349006.

Sequence in context: A062625 A175986 A296351 * A101006 A372769 A306632

Adjacent sequences: A349004 A349005 A349006 * A349008 A349009 A349010

Keyword

nonn

Author

Jaroslav Krizek, Nov 05 2021

Status

approved