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A363027
Sum of divisors of 5*n-4 of form 5*k+2.
5
0, 2, 0, 2, 7, 2, 0, 14, 0, 2, 17, 9, 0, 24, 0, 2, 27, 2, 7, 46, 0, 2, 37, 2, 0, 51, 0, 19, 47, 2, 0, 66, 7, 2, 57, 24, 0, 64, 0, 9, 67, 2, 0, 113, 17, 2, 84, 2, 0, 84, 0, 34, 87, 9, 0, 106, 0, 24, 97, 39, 7, 121, 0, 2, 107, 2, 0, 175, 0, 2, 144, 2, 0, 124, 7, 49, 127, 2, 17, 168, 0, 9, 137, 86, 0, 144, 0, 2
OFFSET
1,2
LINKS
FORMULA
a(n) = A284280(5*n-4).
G.f.: Sum_{k>0} (5*k-3) * x^(3*k-1) / (1 - x^(5*k-3)).
MAPLE
f:= n ->
convert(select(t -> t mod 5 = 2, numtheory:-divisors(5*n-4)), `+`):
map(f, [$1..100]); # Robert Israel, Jul 23 2023
MATHEMATICA
a[n_] := DivisorSum[5*n - 4, # &, Mod[#, 5] == 2 &]; Array[a, 100] (* Amiram Eldar, Jul 06 2023 *)
PROG
(PARI) a(n) = sumdiv(5*n-4, d, (d%5==2)*d);
CROSSREFS
KEYWORD
nonn,look
AUTHOR
Seiichi Manyama, Jul 06 2023
STATUS
approved