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A005072
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Sum of cubes of primes = 1 mod 3 dividing n.
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5
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0, 0, 0, 0, 0, 0, 343, 0, 0, 0, 0, 0, 2197, 343, 0, 0, 0, 0, 6859, 0, 343, 0, 0, 0, 0, 2197, 0, 343, 0, 0, 29791, 0, 0, 0, 343, 0, 50653, 6859, 2197, 0, 0, 343, 79507, 0, 0, 0, 0, 0, 343, 0, 0, 2197, 0, 0, 0, 343, 6859, 0, 0, 0, 226981, 29791, 343, 0, 2197, 0, 300763, 0, 0, 343, 0, 0, 389017, 50653, 0, 6859, 343, 2197, 493039
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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^3 if p = 1 (mod 3), 0 otherwise.
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MATHEMATICA
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f[p_, e_] := If[Mod[p, 3] == 1, p^3, 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])%3) == 1, p^3)); \\ Michel Marcus, Jul 10 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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