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A097022
a(n) = (sigma(2n^2)-3)/6.
3
0, 2, 6, 10, 15, 32, 28, 42, 60, 77, 66, 136, 91, 142, 201, 170, 153, 302, 190, 325, 370, 332, 276, 552, 390, 457, 546, 598, 435, 1007, 496, 682, 864, 767, 883, 1270, 703, 952, 1189, 1317, 861, 1852, 946, 1396, 1875, 1382, 1128, 2216, 1400, 1952, 1995, 1921
OFFSET
1,2
COMMENTS
LINKS
FORMULA
a(n) = (A065765(n)-3)/6 = A000203(A001105(n) - 3)/6.
Sum_{k=1..n} a(k) ~ c * n^3, where c = 4*zeta(3)/Pi^2 = 0.243587... . - Amiram Eldar, Oct 28 2022
MATHEMATICA
Table[(DivisorSigma[1, 2n^2]-3)/6, {n, 60}] (* Harvey P. Dale, Sep 12 2022 *)
PROG
(PARI) a(n) = (sigma(2*n^2) - 3)/6; \\ Michel Marcus, Dec 20 2013
KEYWORD
nonn
AUTHOR
Labos Elemer, Aug 24 2004
STATUS
approved