A321832 a(n) = Sum_{d|n, n/d==1 (mod 4)} d^8 - Sum_{d|n, n/d==3 (mod 4)} d^8.

1, 256, 6560, 65536, 390626, 1679360, 5764800, 16777216, 43040161, 100000256, 214358880, 429916160, 815730722, 1475788800, 2562506560, 4294967296, 6975757442, 11018281216, 16983563040, 25600065536, 37817088000, 54875873280, 78310985280, 110058536960, 152588281251, 208827064832

Offset: 1

Author

N. J. A. Sloane, Nov 24 2018

Keywords

• nonn
• easy
• mult

Links

• Seiichi Manyama, Table of n, a(n) for n = 1..10000
• J. W. L. Glaisher, On the representations of a number as the sum of two, four, six, eight, ten, and twelve squares, Quart. J. Math. 38 (1907), 1-62 (see p. 4 and p. 8).
• Index entries for sequences mentioned by Glaisher.

Crossrefs

Cf. A101455, A258816.

Cf. A321543 - A321565, A321807 - A321836 for similar sequences.

Glaisher's E'_i (i=0..12): A002654, A050469, A050470, A050471, A050468, A321829, A321830, A321831, this sequence, A321833, A321834, A321835, A321836.

Programs

Mathematica

s[n_,r_] := DivisorSum[n, #^8 &, Mod[n/#,4]==r &]; a[n_] := s[n,1] - s[n,3]; Array[a, 30] (* Amiram Eldar, Nov 26 2018 *)
s[n_] := If[OddQ[n], (-1)^((n-1)/2), 0]; (* A101455 *)
f[p_, e_] := (p^(8*e+8) - s[p]^(e+1))/(p^8 - s[p]); a[1] = 1; a[n_] := Times @@ f @@@ FactorInteger[n]; Array[a, 100] (* Amiram Eldar, Nov 04 2023 *)

PARI

apply( A321832(n)=factorback(apply(f->f[1]^(8*f[2]+8)\/(f[1]^8+f[1]%4-2),Col(factor(n)))), [1..50]) \\ M. F. Hasler, Nov 26 2018

Formula

G.f.: Sum_{k>=1} k^8*x^k/(1 + x^(2*k)). - Ilya Gutkovskiy, Nov 26 2018

Multiplicative with a(p^e) = round(p^(8e+8)/(p^8 + (p mod 4) - 2)). (Following R. Israel in A321833.) - M. F. Hasler, Nov 26 2018

Sum_{k=1..n} a(k) ~ c * n^9 / 9, where c = 277*Pi^9/8257536 (A258816). - Amiram Eldar, Nov 04 2023

a(n) = Sum_{d|n} (n/d)^8*sin(d*Pi/2). - Ridouane Oudra, Sep 27 2024