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 A348397 a(n) = Sum_{d|n} sigma_[n-d](d), where sigma_[k](n) is the sum of the k-th powers of the divisors of n. 1
 1, 3, 3, 9, 3, 50, 3, 343, 734, 3388, 3, 133959, 3, 827646, 10297073, 33640713, 3, 2579172499, 3, 44822639761, 678610493345, 285312719194, 3, 393067887861756, 95367431640630, 302875123369476, 150094918113956098, 569940024192528003, 3, 105474401758856279784, 3 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Michel Marcus, Table of n, a(n) for n = 1..500 FORMULA a(n) = 3 iff n is prime. - Bernard Schott, Oct 17 2021 EXAMPLE a(6) = 50; a(6) = sigma_[6-1](1) + sigma_[6-2](2) + sigma_[6-3](3) + sigma_[6-6](6) = (1^5) + (1^4 + 2^4) + (1^3 + 3^3) + (6^0 + 6^0 + 6^0 + 6^0) = 50. MATHEMATICA a[n_] := DivisorSum[n, DivisorSigma[n - #, #] &]; Array[a, 30] (* Amiram Eldar, Oct 17 2021 *) PROG (PARI) a(n) = sumdiv(n, d, sigma(d, n-d)); \\ Michel Marcus, Oct 18 2021 CROSSREFS Cf. A321141. Sequence in context: A157031 A113213 A088032 * A066572 A307379 A276147 Adjacent sequences: A348394 A348395 A348396 * A348398 A348399 A348400 KEYWORD nonn AUTHOR Wesley Ivan Hurt, Oct 16 2021 STATUS approved

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Last modified March 27 13:28 EDT 2023. Contains 361572 sequences. (Running on oeis4.)