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 A324121 a(n) = gcd(n*d(n), sigma(n)), where d(n) = number of divisors of n (A000005) and sigma(n) = sum of divisors of n (A000203). 9
 1, 1, 2, 1, 2, 12, 2, 1, 1, 2, 2, 4, 2, 8, 12, 1, 2, 3, 2, 6, 4, 4, 2, 12, 1, 2, 4, 56, 2, 24, 2, 3, 12, 2, 4, 1, 2, 4, 4, 10, 2, 48, 2, 12, 6, 8, 2, 4, 3, 3, 12, 2, 2, 24, 4, 8, 4, 2, 2, 24, 2, 8, 2, 1, 4, 48, 2, 6, 12, 16, 2, 3, 2, 2, 2, 4, 4, 24, 2, 2, 1, 2, 2, 112, 4, 4, 12, 4, 2, 18, 28, 24, 4, 8, 20, 36, 2, 3, 6, 1, 2, 24, 2, 2, 24 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Records 1, 2, 12, 56, 112, 120, 336, 720, 992, 2016, 4368, 8640, 14880, 16256, 26208, 59520, 78624, 120960, 131040, 191520, 227584, 297600, ... occur at positions: 1, 3, 6, 28, 84, 120, 140, 270, 496, 672, 1638, 2970, 6200, 8128, 8190, 18600, 27846, 30240, 32760, 55860, 105664, 117800, ... . Note that A001599 is not a subsequence of the latter, as at least 18620 (present in A001599) is missing. LINKS Antti Karttunen, Table of n, a(n) for n = 1..10080 Antti Karttunen, Data supplement: n, a(n) computed for n = 1..117800 FORMULA a(n) = gcd(A000203(n), A038040(n)). a(n) = A324058(A156552(n)). PROG (PARI) A324121(n) = gcd(sigma(n), n*numdiv(n)); CROSSREFS Cf. A000005, A000203, A001599, A038040, A106315, A106316, A156552, A324045, A324046, A324047, A324058, A324122. Sequence in context: A324058 A165313 A325636 * A320834 A052579 A266314 Adjacent sequences:  A324118 A324119 A324120 * A324122 A324123 A324124 KEYWORD nonn AUTHOR Antti Karttunen, Feb 15 2019 STATUS approved

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Last modified August 11 00:32 EDT 2020. Contains 336403 sequences. (Running on oeis4.)