A166660 Totally multiplicative sequence with a(p) = 2p+1 for prime p.

1, 5, 7, 25, 11, 35, 15, 125, 49, 55, 23, 175, 27, 75, 77, 625, 35, 245, 39, 275, 105, 115, 47, 875, 121, 135, 343, 375, 59, 385, 63, 3125, 161, 175, 165, 1225, 75, 195, 189, 1375, 83, 525, 87, 575, 539, 235, 95, 4375, 225, 605

Offset: 1

Author

Jaroslav Krizek, Oct 18 2009

Keywords

• nonn
• mult

Links

• G. C. Greubel, Table of n, a(n) for n = 1..10000

Programs

Mathematica

a[1] = 1; a[n_] := (fi = FactorInteger[n]; Times @@ ((2*fi[[All, 1]] + 1)^fi[[All, 2]]) ); Table[a[n], {n, 1, 100}](* G. C. Greubel, May 21 2016 *)

Formula

Multiplicative with a(p^e) = (2p+1)^e. If n = Product p(k)^e(k) then a(n) = Product (2*p(k)+1)^e(k).