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A128216
a(1)=a(2)=1. a(n+1) = a(n) + a(smallest prime dividing n).
2
1, 1, 2, 4, 5, 10, 11, 22, 23, 25, 26, 52, 53, 106, 107, 109, 110, 220, 221, 442, 443, 445, 446, 892, 893, 898, 899, 901, 902, 1804, 1805, 3610, 3611, 3613, 3614, 3619, 3620, 7240, 7241, 7243, 7244, 14488, 14489, 28978, 28979, 28981, 28982, 57964, 57965
OFFSET
1,3
LINKS
EXAMPLE
The smallest prime dividing 12 is 2. So a(13) = a(12) + a(2) = 52 + 1 = 53.
MAPLE
with(numtheory): a[1]:=1:a[2]:=1:for n from 2 to 55 do a[n+1]:=a[n]+a[factorset(n)[1]] od: seq(a[n], n=1..55); # Emeric Deutsch, Mar 07 2007
MATHEMATICA
a128216[1] = 1; a128216[2] = 1;
a128216[n_] := a128216[n] = a128216[n-1] + a128216[First[First[FactorInteger[n-1]]]];
Array[a128216, 49] (* data *) (* Hartmut F. W. Hoft, Mar 08 2017 *)
CROSSREFS
Sequence in context: A109511 A018339 A328009 * A299322 A365501 A080735
KEYWORD
nonn
AUTHOR
Leroy Quet, Feb 19 2007
EXTENSIONS
More terms from Emeric Deutsch, Mar 07 2007
STATUS
approved