OFFSET
1,2
MATHEMATICA
f[n_] := Module[{s = NestWhileList[n * DivisorSigma[0, #] &, 1, UnsameQ, All]}, Differences[Position[s, s[[-1]]]][[1, 1]]]; seq[len_, nmax_] := Module[{v = Table[0, {len}], n = 1, c = 0, i}, While[c < len && n < nmax, i = f[n]; If[i <= len && v[[i]] == 0, c++; v[[i]] = n]; n++]; TakeWhile[v, # > 0 &]]; seq[15, 10^6] (* Amiram Eldar, Nov 17 2021 *)
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Tejo Vrush, Nov 17 2021
EXTENSIONS
Escape clause value changed to -1. - N. J. A. Sloane, Jan 14 2022
STATUS
approved