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A005072 Sum of cubes of primes = 1 mod 3 dividing n. 5
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 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,7
LINKS
FORMULA
Additive with a(p^e) = p^3 if p = 1 (mod 3), 0 otherwise.
MATHEMATICA
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 *)
PROG
(Scheme) (define (A005072 n) (if (= 1 n) 0 (+ (A000578 (if (= 1 (modulo (A020639 n) 3)) (A020639 n) 0)) (A005072 (A028234 n))))) ;; Antti Karttunen, Jul 09 2017
(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
CROSSREFS
Sequence in context: A023909 A035844 A028681 * A112821 A045130 A045269
KEYWORD
nonn
AUTHOR
EXTENSIONS
More terms from Antti Karttunen, Jul 09 2017
STATUS
approved

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Last modified May 27 12:23 EDT 2024. Contains 372858 sequences. (Running on oeis4.)