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 A350073 a(n) = A064989(sigma(n)), where A064989 is multiplicative with a(2^e) = 1 and a(p^e) = prevprime(p)^e for odd primes p. 10
 1, 2, 1, 5, 2, 2, 1, 6, 11, 4, 2, 5, 5, 2, 2, 29, 4, 22, 3, 10, 1, 4, 2, 6, 29, 10, 3, 5, 6, 4, 1, 20, 2, 8, 2, 55, 17, 6, 5, 12, 10, 2, 7, 10, 22, 4, 2, 29, 34, 58, 4, 25, 8, 6, 4, 6, 3, 12, 6, 10, 29, 2, 11, 113, 10, 4, 13, 20, 2, 4, 4, 66, 31, 34, 29, 15, 2, 10, 3, 58, 49, 20, 10, 5, 8, 14, 6, 12, 12, 44, 5, 10 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Antti Karttunen, Table of n, a(n) for n = 1..20000 Index entries for sequences computed from indices in prime factorization Index entries for sequences related to sigma(n) FORMULA Multiplicative with a(p^e) = A064989(1 + p + p^2 + ... + p^e). a(n) = A064989(A000203(n)) = A064989(A161942(n)). MATHEMATICA f[2, e_] := 1; f[p_, e_] := NextPrime[p, -1]^e; a[1] = 1; a[n_] := Times @@ f @@@ FactorInteger[DivisorSigma[1, n]]; Array[a, 100] (* Amiram Eldar, Dec 12 2021 *) PROG (PARI) A064989(n) = { my(f = factor(n)); for (i=1, #f~, f[i, 1] = if(2==f[i, 1], 1, precprime(f[i, 1]-1))); factorback(f); }; A350073(n) = A064989(sigma(n)); CROSSREFS Cf. A000203, A064989, A161942, A337343 (a(n) >= n), A348748, A348749. Cf. also A326042, A350072. Sequence in context: A281348 A308698 A308569 * A174978 A110874 A010253 Adjacent sequences: A350070 A350071 A350072 * A350074 A350075 A350076 KEYWORD nonn,mult AUTHOR Antti Karttunen, Dec 12 2021 STATUS approved

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Last modified December 5 03:25 EST 2023. Contains 367567 sequences. (Running on oeis4.)