A072542 a(n) = the least positive integer k such that sigma(k) > sigma(1) + ... + sigma(n).

2, 4, 6, 10, 12, 18, 20, 24, 30, 36, 48, 60, 60, 60, 72, 84, 96, 108, 120, 120, 144, 168, 168, 180, 180, 210, 240, 240, 240, 288, 288, 300, 336, 336, 360, 360, 360, 420, 420, 420, 480, 480, 504, 540, 600, 600, 600, 660, 660, 720, 720, 720, 720, 840, 840, 840

Offset

1,1

Links

Table of n, a(n) for n=1..56.

Example

sigma(1) + ... + sigma(4) = 15 and k = 10 is the least positive integer such that sigma(k) > 15. Hence a(4) = 10.

Mathematica

s = 0; a = {}; For[i = 1, i <= 100, i++, s = s + DivisorSigma[1, i]; k = 1; While[DivisorSigma[1, k] <= s, k = k + 1]; a = Append[a, k]]; a
Module[{k=1}, While[DivisorSigma[1, k]<=#, k++]; k]&/@Accumulate[DivisorSigma[1, Range[60]]] (* Harvey P. Dale, May 28 2026 *)

Crossrefs

Sequence in context: A220478 A033868 A045954 * A167856 A293750 A162578

Adjacent sequences: A072539 A072540 A072541 * A072543 A072544 A072545

Keyword

nonn

Author

Joseph L. Pe, Dec 08 2002

Status

approved