A371922 Indices of records in A371921: numbers k such that A371921(k) > A371921(m) for all m < k.
1, 12, 24, 90, 204, 330, 540, 1080, 1140, 2184, 3480, 6324, 15630, 23496, 38340, 48510, 56760, 99636, 234960, 270180, 300150, 528180, 703080, 973644, 1907178, 5992380, 7980930, 12032640, 20687436, 23847642, 27465840, 28653720, 34964340
Offset: 1
Examples
The iterations of A033880 over the first 8 terms: n | a(n) | Iterations --+------+---------------------------------------------------------------- 1 | 1 | 1 -> -1 2 | 12 | 12 -> 4 -> -1 3 | 24 | 24 -> 12 -> 4 -> -1 4 | 90 | 90 -> 54 -> 12 -> 4 -> -1 5 | 204 | 204 -> 96 -> 60 -> 48 -> 28 -> 0 6 | 330 | 330 -> 204 -> 96 -> 60 -> 48 -> 28 -> 0 7 | 540 | 540 -> 600 -> 660 -> 696 -> 408 -> 264 -> 192 -> 124 -> -24 8 | 1080 | 1080 -> 1440 -> 2034 -> 378 -> 204 -> 96 -> 60 -> 48 -> 28 -> 0
Links
- Amiram Eldar, Table of n, a(n), A371921(a(n)) for n = 1..33.
Programs
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Mathematica
ab[n_] := Module[{k}, If[n < 1, 0, k = DivisorSigma[1, n] - 2*n; If[k < 1, 0, k]]]; f[n_] := Module[{s = NestWhileList[ab, n, UnsameQ, All]}, If[s[[-1]] == 0, Length[s] - 2, 0]]; seq[max_] := Module[{fm = 0, f1, s = {}}, Do[f1 = f[n]; If[f1 > fm, fm = f1; AppendTo[s, n]], {n, 1, max}]; s]; seq[10^5] -
PARI
ab(n) = {my(k); if(n < 1, 0, k = sigma(n) - 2*n; if(k < 1, 0, k));} f(n) = {my(t = 0); until(bittest(t, n = ab(n)), t += 1<
Comments