OFFSET
0,1
COMMENTS
Records: 2, 6, 27, 121, 301, 930, 1273, 4863, 9216, 19692, 25442, 83161, 100652, 226181, 419248, 744796, 3739690, 4238314, etc. - Robert G. Wilson v, Sep 23 2017
Indices of records: 0, 1, 3, 6, 7, 8, 12, 14, 16, 18, 20, 25, 26, 27, 30, 32, 46, 47, 48, 49, 50, 56, 57, 58, 59, 61, 63, 65, 67, 76, 77, 78, 82, 83, 84, 85, etc. - Robert G. Wilson v, Sep 23 2017
Checked through a(138)=60780636903. - Hugo Pfoertner, Nov 15 2017
LINKS
Hugo Pfoertner, Table of n, a(n) for n = 0..138 (terms up to 66 from David W. Wilson, 67-100 from Robert G. Wilson v and Charles R Greathouse IV).
MATHEMATICA
f[n_] := Plus @@ Divisors@ n -1; g[n_] := Length@ NestWhileList[f@# &, n, !PrimeQ@# &] - 1; t[_] := -1; k = 2; While[k < 10000001, a = g[k]; If[ t@ a == -1, t@ a = k; Print[{a, k}]]; k++]; t@# & /@ Range[0, 50] (* Robert G. Wilson v, Sep 22 2017 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved