A002954 Smallest number such that n-th iterate of Chowla function is 0. (Formerly M1099)

2, 4, 8, 15, 12, 27, 24, 36, 90, 96, 245, 288, 368, 676, 1088, 2300, 1596, 1458, 3344, 3888, 5360, 8895, 11852, 25971, 23360, 38895, 35540, 35595, 36032, 53823, 47840, 62055, 59360, 83391, 70784, 128079, 145668, 349299, 254540, 327495, 293744, 328335, 167664

Offset

1,1

Comments

Chowla's function (A048050) = sum of divisors of n except 1 and n.

a(83) > 10^10. - Donovan Johnson, Feb 15 2013

The first 35 terms were found by Lal and Forbes (1971). - Amiram Eldar, Mar 09 2024

References

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

Donovan Johnson, Table of n, a(n) for n = 1..82

M. Lal and A. Forbes, A note on Chowla's function, Math. Comp., 25 (1971), 923-925.

Mathematica

chowla[n_] := DivisorSigma[1, n] - 1 - n; chowlaSeq[n_] := Module[{m = n, cnt = 0, seq = {}}, While[m > 0 && ! MemberQ[seq, m], AppendTo[seq, m]; m = chowla[m]; cnt++]; If[m == 0, AppendTo[seq, m]]; seq]; nn = 20; t = Table[0, {nn}]; left = nn; n = 1; While[left > 0, n++; cSeq = chowlaSeq[n]; c = Length[cSeq] - 1; If[cSeq[[-1]] == 0 && c <= nn && t[[c]] == 0, t[[c]] = n; left--]]; t (* T. D. Noe, Dec 29 2011 *)

Crossrefs

Cf. A048050.

Sequence in context: A118897 A098056 A097100 * A019278 A267894 A084345

Adjacent sequences: A002951 A002952 A002953 * A002955 A002956 A002957

Keyword

nonn

Author

N. J. A. Sloane

Extensions

a(31)-a(43) from T. D. Noe, Dec 29 2011

Status

approved