OFFSET
0,7
LINKS
Amiram Eldar, Table of n, a(n) for n = 0..10000
K. S. Williams, The parents of Jacobi's four squares theorem are unique, Amer. Math. Monthly, 120 (2013), 329-345.
MAPLE
s := proc(n, k)
if modp(n, k) = 0 then
numtheory[sigma](n/k) ;
else
0 ;
end if;
end proc:
A224226 := proc(n)
if n = 0 then
1;
else
s(n, 3)-s(n, 4)-s(n, 6)+s(n, 12) ;
end if;
end proc: # R. J. Mathar, Nov 14 2018
MATHEMATICA
s[n_, k_] := If[Divisible[n, k], DivisorSigma[1, n/k], 0]; a[0] = 1; a[n_] := s[n, 3] - s[n, 4] - s[n, 6] + s[n, 12]; Array[a, 100, 0] (* Amiram Eldar, Aug 17 2019 *)
PROG
(PARI) s(n, k) = if (!(n%k), sigma(n/k), 0);
a(n) = if (n==0, 1, s(n, 3)-s(n, 4)-s(n, 6)+s(n, 12)); \\ Michel Marcus, Sep 27 2017
CROSSREFS
KEYWORD
sign
AUTHOR
N. J. A. Sloane, Apr 09 2013
STATUS
approved