A131907 Integers for which a smaller positive integer exists which has the same sum of cubes of its divisors.

194315, 295301, 2953010, 1181204, 1476505, 1886920, 2067107, 2362408, 2526095, 2953010, 3248311, 3691985, 3838913, 4134214, 4469245, 4724816, 5020117, 5610719, 5635135, 5906020, 6023765, 6496622, 6791923, 7382525, 7677826

Offset

1,1

Comments

If i < j and A001158(i) = A001158(j) then j is in this sequence. - Jason Yuen, Sep 22 2024

Links

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

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

Formula

n-th element of {x>0: there exists a k with 0<k<x and the same sum of the cubes of its divisors as x}.

Example

194315 is in this sequence because A001158(184926) = A001158(194315) = 7401260364550416.

Mathematica

First@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. A001158, A069822, A131902-A131908.

Sequence in context: A254995 A232202 A344630 * A202937 A013901 A206052

Adjacent sequences: A131904 A131905 A131906 * A131908 A131909 A131910

Keyword

nonn,changed

Author

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

Extensions

More terms from Max Alekseyev and Daniel Lichtblau (danl(AT)wolfram.com), Jul 28 2007

Status

approved