A128215 a(1)=a(2)=1. a(n+1) = a(n) + a(largest prime dividing n).

1, 1, 2, 4, 5, 10, 12, 24, 25, 27, 32, 64, 66, 132, 144, 149, 150, 300, 302, 604, 609, 621, 653, 1306, 1308, 1313, 1379, 1381, 1393, 2786, 2791, 5582, 5583, 5615, 5765, 5777, 5779, 11558, 11860, 11926, 11931, 23862, 23874, 47748, 47780, 47785, 48438, 96876

Offset

1,3

Links

Giovanni Resta, Table of n, a(n) for n = 1..10000

Example

The largest prime dividing 12 is 3. So a(13) = a(12) + a(3) = 64 + 2 = 66.

Maple

with(numtheory): a[1]:=1:a[2]:=1:for n from 2 to 55 do a[n+1]:=a[n]+a[factorset(n)[nops(factorset(n))]] od: seq(a[n], n=1..55); # Emeric Deutsch, Mar 07 2007

Mathematica

a128215[1] = 1; a128215[2] = 1;
a128215[n_] := a128215[n] = a128215[n-1] + a128215[First[Last[FactorInteger[n-1]]]];
Array[a128215, 48] (* data *) (* Hartmut F. W. Hoft, Mar 08 2017 *)

Crossrefs

Cf. A128216, A006530.

Sequence in context: A133732 A328221 A364913 * A325676 A097132 A321683

Adjacent sequences: A128212 A128213 A128214 * A128216 A128217 A128218

Keyword

nonn

Author

Leroy Quet, Feb 19 2007

Extensions

More terms from Emeric Deutsch, Mar 07 2007

Status

approved