OFFSET
1,2
LINKS
G. C. Greubel, Table of n, a(n) for n = 1..10000
FORMULA
From Amiram Eldar, Nov 18 2023: (Start)
a(n) = Sum_{d|n} Kronecker(-47, d).
Multiplicative with a(47^e) = 1, a(p^e) = (1+(-1)^e)/2 if Kronecker(-47, p) = -1, and a(p^e) = e+1 if Kronecker(-47, p) = 1.
Asymptotic mean: Limit_{m->oo} (1/m) * Sum_{k=1..m} a(k) = 5*Pi/sqrt(47) = 2.291241... . (End)
MATHEMATICA
a[n_] := If[n < 0, 0, DivisorSum[n, KroneckerSymbol[-47, #] &]];
Table[a[n], {n, 1, 100}] (* G. C. Greubel, Apr 25 2018 *)
PROG
(PARI) my(m=-47); direuler(p=2, 101, 1/(1-(kronecker(m, p)*(X-X^2))-X))
(PARI) a(n) = sumdiv(n, d, kronecker(-47, d)); \\ Amiram Eldar, Nov 18 2023
CROSSREFS
KEYWORD
nonn,easy,mult
AUTHOR
STATUS
approved