OFFSET
1,5
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..10000
FORMULA
Additive with a(p^e) = p if p = 1 (mod 4), 0 otherwise.
MATHEMATICA
Array[DivisorSum[#, # &, And[PrimeQ@ #, Mod[#, 4] == 1] &] &, 101] (* Michael De Vlieger, Jul 11 2017 *)
f[p_, e_] := If[Mod[p, 4] == 1, p, 0]; a[n_] := Plus @@ f @@@ FactorInteger[n]; a[1] = 0; Array[a, 100] (* Amiram Eldar, Jun 21 2022 *)
PROG
(PARI) a(n)=my(f=factor(n)[, 1]); sum(i=1, #f, if(f[i]%4==1, f[i])) \\ Charles R Greathouse IV, Mar 11 2014
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
More terms from Antti Karttunen, Jul 11 2017
STATUS
approved