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 A067577 a(n) = Product_{i=1..n} sigma(i) * Sum_{i=1..n} 1/sigma(i). 1
 1, 4, 19, 145, 954, 11952, 101664, 1573344, 21179232, 390661056, 4857760512, 138055228416, 1989835352064, 48554918608896, 1184490930438144, 37179368055373824, 683493250562260992, 26913000032107757568, 548273767789158727680, 23227773590084738088960, 751700319286194622955520 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Michael De Vlieger, Table of n, a(n) for n = 1..419 MATHEMATICA Array[Product[DivisorSigma[1, i], {i, #}]*Sum[1/DivisorSigma[1, j], {j, #}] &, 21] (* Michael De Vlieger, Jul 16 2022 *) PROG (PARI) a(n) = prod(i=1, n, sigma(i)) * sum(i=1, n, 1/sigma(i)); \\ Michel Marcus, Jan 09 2021 CROSSREFS Cf. A000203 (sigma), A066780, A212717, A212718. Sequence in context: A208992 A321388 A212717 * A225904 A203010 A362380 Adjacent sequences: A067574 A067575 A067576 * A067578 A067579 A067580 KEYWORD nonn AUTHOR Benoit Cloitre, Jan 30 2002 EXTENSIONS More terms from Michel Marcus, Jan 09 2021 STATUS approved

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Last modified September 22 21:28 EDT 2023. Contains 365531 sequences. (Running on oeis4.)