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

Author

Hans Havermann, Aug 24 2016

Keywords

• nonn

Examples

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

Crossrefs

Cf. A106490.

Programs

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 *)

Extensions

More terms from Alois P. Heinz, Aug 25 2016