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%I M1099 #31 Mar 09 2024 04:43:12
%S 2,4,8,15,12,27,24,36,90,96,245,288,368,676,1088,2300,1596,1458,3344,
%T 3888,5360,8895,11852,25971,23360,38895,35540,35595,36032,53823,47840,
%U 62055,59360,83391,70784,128079,145668,349299,254540,327495,293744,328335,167664
%N Smallest number such that n-th iterate of Chowla function is 0.
%C Chowla's function (A048050) = sum of divisors of n except 1 and n.
%C a(83) > 10^10. - _Donovan Johnson_, Feb 15 2013
%C The first 35 terms were found by Lal and Forbes (1971). - _Amiram Eldar_, Mar 09 2024
%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H Donovan Johnson, <a href="/A002954/b002954.txt">Table of n, a(n) for n = 1..82</a>
%H M. Lal and A. Forbes, <a href="http://dx.doi.org/10.1090/S0025-5718-1971-0297685-X">A note on Chowla's function</a>, Math. Comp., 25 (1971), 923-925.
%t 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 *)
%Y Cf. A048050.
%K nonn
%O 1,1
%A _N. J. A. Sloane_
%E a(31)-a(43) from _T. D. Noe_, Dec 29 2011
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