A233510 Least number k such that the number of iterations of h(m) = (greatest prime divisor of m) - (least prime divisor of m) that map k to 0 is n; see Comments.

1, 6, 34, 82, 226, 687, 3027, 12387, 28738, 258627, 1109487, 2218978, 13313877, 26627758, 159766557, 2929053434

Offset

1,2

Comments

The domain of h is extended to include 1, with h(1) = 1 (as in Mathematica).

a(17) <= 51096502407. - Donovan Johnson, Dec 15 2013

Links

Table of n, a(n) for n=1..16.

Example

h(6) = 3 - 2 = 1, and h(1) = 0, so a(2) = 6.

Mathematica

z = 1000000; h[n_] := h[n] = FactorInteger[n][[-1, 1]] - FactorInteger[n][[1, 1]]; t[n_] := t[n] = Drop[FixedPointList[h, n], -2]; Table[t[n], {n, 1, z}]; a = Table[Length[t[n]], {n, 1, z}]; f[n_] := First[Flatten[Position[a, n]]]; g = Table[f[n], {n, 1, 10}]

Crossrefs

Cf. A231813.

Sequence in context: A152528 A135733 A072312 * A296808 A319199 A305164

Adjacent sequences: A233507 A233508 A233509 * A233511 A233512 A233513

Keyword

nonn,more

Author

Clark Kimberling, Dec 11 2013

Extensions

a(11)-a(16) from Donovan Johnson, Dec 15 2013

Status

approved