A131908 Smallest positive integer k with the same sum of cubes of divisors as the n-th integer for which such a k exists.

184926, 291741, 583482, 1166964, 1458705, 1880574, 2042187, 2333928, 2404038, 2917410, 3209151, 3513594, 3792633, 4084374, 4253298, 4667856, 4959597, 5543079, 5362854, 5834820, 5732706, 6418302, 6710043, 7293525, 7585266

Offset

1,1

Links

Table of n, a(n) for n=1..25.

Max Alekseyev, List of first 224 pairs A131907(n), A131908(n)

Formula

a(n)=min(k>0, k has the same sum of cubes of divisors as A131907(n))

Example

a(1)=184926 because A131907(1)=194315 with the sum of cubes of its divisors being 7401260364550416. This is the same as the sum of cubes of divisors of 184926 and there is no positive integer less than 184926 with this cubesum of its divisors

Mathematica

Last@Transpose[Reap[For[n = 1, n <= 5*10^6, n++, (If[Head[ #1] === tmp, #1 = n, Sow[{n, #1}]] & )[ tmp[DivisorSigma[3, n]]]]][[2, 1]]]

Crossrefs

Cf. A069822, A131902-A131907.

Sequence in context: A244173 A245795 A251449 * A234409 A254772 A254779

Adjacent sequences: A131905 A131906 A131907 * A131909 A131910 A131911

Keyword

nonn

Author

Peter Pein (petsie(AT)dordos.net), Jul 26 2007, Jul 28 2007

Extensions

More terms from Max Alekseyev, Jul 28 2007

Status

approved