A276230 a(n) is the A106490 index where n first occurs.

1, 2, 4, 12, 36, 144, 720, 3600, 25200, 176400, 1587600, 17463600, 192099600, 2497294800, 32464832400, 551902150800, 9382336563600, 178264394708400, 3387023499459600, 77901540487570800, 1791735431214128400, 44793385780353210000, 1299008187630243090000

Offset

0,2

Links

Table of n, a(n) for n=0..22.

Example

0, 1, 2, and 3 first appear in A106490 at positions 1, 2, 4, and 12, respectively.

Mathematica

a[n_] := a[n] = If[n == 1, 0, Sum[1 + a[i[[2]]], {i, FactorInteger[n]}]];
Flatten@ Table[FirstPosition[#, k_ /; k == n], {n, 0, 9}] &@ Table[a[n], {n, 10^6}] (* Michael De Vlieger, Aug 25 2016, Version 10, after Jean-François Alcover at A106490 *)

Crossrefs

Cf. A106490.

Sequence in context: A111942 A010551 A349282 * A003701 A255432 A275539

Adjacent sequences: A276227 A276228 A276229 * A276231 A276232 A276233

Keyword

nonn

Author

Hans Havermann, Aug 24 2016

Extensions

More terms from Alois P. Heinz, Aug 25 2016

Status

approved