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A005071
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Sum of squares of primes = 1 mod 3 dividing n.
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5
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0, 0, 0, 0, 0, 0, 49, 0, 0, 0, 0, 0, 169, 49, 0, 0, 0, 0, 361, 0, 49, 0, 0, 0, 0, 169, 0, 49, 0, 0, 961, 0, 0, 0, 49, 0, 1369, 361, 169, 0, 0, 49, 1849, 0, 0, 0, 0, 0, 49, 0, 0, 169, 0, 0, 0, 49, 361, 0, 0, 0, 3721, 961, 49, 0, 169, 0, 4489, 0, 0, 49, 0, 0, 5329, 1369, 0, 361, 49, 169, 6241, 0, 0, 0, 0, 49, 0, 1849, 0, 0, 0, 0, 218
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OFFSET
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1,7
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LINKS
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FORMULA
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Additive with a(p^e) = p^2 if p = 1 (mod 3), 0 otherwise.
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MATHEMATICA
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Module[{sp=Select[Prime[Range[100]], Mod[#, 3]==1&]}, Table[Total[ Select[ sp, Divisible[ n, #]&]^2], {n, 70}]] (* Harvey P. Dale, Dec 19 2014 *)
f[p_, e_] := If[Mod[p, 3] == 1, 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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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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