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 A325470 a(n) is the sum of divisors d of n such that d divides sigma(d). 4
 1, 1, 1, 1, 1, 7, 1, 1, 1, 1, 1, 7, 1, 1, 1, 1, 1, 7, 1, 1, 1, 1, 1, 7, 1, 1, 1, 29, 1, 7, 1, 1, 1, 1, 1, 7, 1, 1, 1, 1, 1, 7, 1, 1, 1, 1, 1, 7, 1, 1, 1, 1, 1, 7, 1, 29, 1, 1, 1, 7, 1, 1, 1, 1, 1, 7, 1, 1, 1, 1, 1, 7, 1, 1, 1, 1, 1, 7, 1, 1, 1, 1, 1, 35, 1, 1 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,6 LINKS Antti Karttunen, Table of n, a(n) for n = 1..20000 FORMULA a(A097603(n)) > 1. EXAMPLE For n = 12, divisors d of 12: 1, 2, 3, 4, 6, 12; corresponding sigma(d): 1, 3, 4, 7, 12, 28; d divides sigma(d) for 2 divisors d: 1 and 6; a(12) = 1 + 6 = 7. MATHEMATICA a[n_] := DivisorSum[n, # &, Divisible[DivisorSigma[1, #], #] &];  Array[a, 100] (* Amiram Eldar, Aug 17 2019 *) PROG (MAGMA) [&+[d: d in Divisors(n) | IsIntegral(SumOfDivisors(d) / d)] : n in [1..100]] (PARI) a(n)={sumdiv(n, d, if(sigma(d) % d == 0, d))} \\ Andrew Howroyd, Aug 16 2019 CROSSREFS Cf. A000203, A097603, A325469, A325471. Sequence in context: A101027 A129408 A339748 * A240831 A170824 A248909 Adjacent sequences:  A325467 A325468 A325469 * A325471 A325472 A325473 KEYWORD nonn AUTHOR Jaroslav Krizek, Aug 16 2019 STATUS approved

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Last modified June 14 19:28 EDT 2021. Contains 345038 sequences. (Running on oeis4.)