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A005083
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Sum of squares of primes = 3 mod 4 dividing n.
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7
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0, 0, 9, 0, 0, 9, 49, 0, 9, 0, 121, 9, 0, 49, 9, 0, 0, 9, 361, 0, 58, 121, 529, 9, 0, 0, 9, 49, 0, 9, 961, 0, 130, 0, 49, 9, 0, 361, 9, 0, 0, 58, 1849, 121, 9, 529, 2209, 9, 49, 0, 9, 0, 0, 9, 121, 49, 370, 0, 3481, 9, 0, 961, 58, 0, 0, 130, 4489, 0, 538, 49, 5041, 9, 0, 0, 9, 361, 170, 9, 6241, 0, 9, 0, 6889, 58
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OFFSET
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1,3
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LINKS
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FORMULA
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Additive with a(p^e) = p^2 if p = 3 (mod 4), 0 otherwise.
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MATHEMATICA
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Array[DivisorSum[#, #^2 &, And[PrimeQ@ #, Mod[#, 4] == 3] &] &, 84] (* Michael De Vlieger, Jul 11 2017 *)
f[p_, e_] := If[Mod[p, 4] == 3, p^2, 0]; a[n_] := Plus @@ f @@@ FactorInteger[n]; a[1] = 0; Array[a, 100] (* Amiram Eldar, Jun 21 2022 *)
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PROG
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(PARI) a(n) = my(f=factor(n)); sum(k=1, #f~, if (((p=f[k, 1])%4) == 3, p^2)); \\ Michel Marcus, Jul 11 2017
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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