OFFSET
1,6
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
FORMULA
From Amiram Eldar, Nov 05 2023: (Start)
Sum_{k=1..n} a(k) ~ c * n^3 / 3, where c = 7*zeta(3)/16 - Pi^3/64 = 0.041426822002... . (End)
MATHEMATICA
a[n_] := DivisorSum[n, #^2 &, Mod[n/#, 4] == 3 &]; Array[a, 100] (* Amiram Eldar, Nov 05 2023 *)
PROG
(Haskell)
a050465 n = sum [d ^ 2 | d <- a027750_row n, mod (div n d) 4 == 3]
-- Reinhard Zumkeller, Mar 06 2012
(PARI) a(n) = sumdiv(n, d, (n/d % 4 == 3) * d^2); \\ Amiram Eldar, Nov 05 2023
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Dec 23 1999
EXTENSIONS
Offset fixed by Reinhard Zumkeller, Mar 06 2012
STATUS
approved