A283237 a(n) = sigma_2(3*n).

10, 50, 91, 210, 260, 455, 500, 850, 820, 1300, 1220, 1911, 1700, 2500, 2366, 3410, 2900, 4100, 3620, 5460, 4550, 6100, 5300, 7735, 6510, 8500, 7381, 10500, 8420, 11830, 9620, 13650, 11102, 14500, 13000, 17220, 13700, 18100, 15470, 22100, 16820, 22750, 18500

Offset: 1

Author

Seiichi Manyama, Mar 03 2017

Keywords

• nonn
• easy

Links

• Seiichi Manyama, Table of n, a(n) for n = 1..10000

Crossrefs

Sigma_2(k*n): A001157 (k=1), A099979 (k=2), this sequence (k=3).

Cf. A002117.

Programs

Mathematica

Table[DivisorSigma[2,3n],{n,1,43}] (* Indranil Ghosh, Mar 03 2017 *)

PARI

a(n) = sigma(3*n,2); \\ Indranil Ghosh, Mar 03 2017

Formula

a(n) = A001157(3*n).

Sum_{k=1..n} a(k) ~ (29*zeta(3)/9) * n^3. - Amiram Eldar, Dec 12 2023