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 A266999 Smallest number m such that A266998(m) = n. 3
 1, 10, 4, 12, 6, 3, 2, 11, 5, 18, 7, 13, 9, 19, 8, 17, 115, 3789 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS The next term is too large to include. LINKS Michel Marcus, Table of n, a(n) for n = 0..17 FORMULA A266998(a(n)) = n and A266998(m) != n for m < a(n). MATHEMATICA a266999={}; f[n_]:=Total[IntegerDigits[n]*(IntegerDigits[n]+1)/2]; g[n_]:=NestWhileList[f[#]&, n, #>1&]; h[n_]:=Length[g[n]]-1; a266998=h/@Range[10^6]; Do[AppendTo[a266999, First[Position[a266998, m]]], {m, 0, Max[a266998]}]; a266999//Flatten PROG (PARI) strd(n) = {my(d = digits(n)); sum(k=1, #d, d[k]*(d[k]+1)/2); } nbi(n) = {my(nb=0); while(n != 1, n = strd(n); nb++; ); nb; } a(n) = {my(m = 1); while(nbi(m) != n, m++); m; } \\ Michel Marcus, Jan 12 2016 CROSSREFS Cf. A266998. Sequence in context: A309707 A100844 A076587 * A166204 A329649 A040094 Adjacent sequences:  A266996 A266997 A266998 * A267000 A267001 A267002 KEYWORD base,more,nonn AUTHOR Ivan N. Ianakiev, Jan 10 2016 STATUS approved

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Last modified December 8 14:38 EST 2019. Contains 329865 sequences. (Running on oeis4.)