A074376 s(3s-1)/2 where s is the sum of the prime factors of n (with repetition).
0, 5, 12, 22, 35, 35, 70, 51, 51, 70, 176, 70, 247, 117, 92, 92, 425, 92, 532, 117, 145, 247, 782, 117, 145, 330, 117, 176, 1247, 145, 1426, 145, 287, 532, 210, 145, 2035, 651, 376, 176, 2501, 210, 2752, 330, 176, 925, 3290, 176, 287, 210, 590, 425, 4187
Offset: 1
Examples
a(20) = 9(3*9-1)/2 = 117 because 9 = 2+2+5 and 20 = 2*2*5.
Links
- Harvey P. Dale, Table of n, a(n) for n = 1..1000
- Neville Holmes, Integer Sequence Combinations [Broken link?]
Programs
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Mathematica
spf[n_]:=Module[{t=Total[Flatten[Table[#[[1]],#[[2]]]&/@FactorInteger[ n]]]},(t(3t-1))/2]; Join[{0},Array[spf,60,2]] (* Harvey P. Dale, Sep 23 2016 *) -
PARI
sopfr(n) = my(f=factor(n)); sum(k=1, matsize(f)[1], f[k, 1]*f[k, 2]) fn(n) = my(s=sopfr(n)); s*(3*s-1)/2 \\ Michel Marcus, Jul 11 2013