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 A247951 a(n) = Product_{i=1..n} sigma_2(i). 3
 1, 5, 50, 1050, 27300, 1365000, 68250000, 5801250000, 527913750000, 68628787500000, 8372712075000000, 1758269535750000000, 298905821077500000000, 74726455269375000000000, 19428878370037500000000000, 6625247524182787500000000000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS a(n) is the product of the sum of the squared divisors of i, for i from 1 to n. LINKS Vaclav Kotesovec, Table of n, a(n) for n = 1..248 Vaclav Kotesovec, Plot (a(n)/(n!)^2)^(1/n) for n = 1..100000 Ramanujan's Papers, Some formulas in the analytic theory of numbers, Messenger of Mathematics, XLV, 1916, 81-84, Formula (20). FORMULA a(n) = Product_{i=1..n} A001157(i). Lim_{n->infinity} (a(n) / (n!)^2)^(1/n) = A345158. - Vaclav Kotesovec, Jun 10 2021 MAPLE with(numtheory): A247951:=n->mul(sigma[2](i), i=1..n): seq(A247951(n), n=1..20); MATHEMATICA Table[Product[DivisorSigma[2, i], {i, n}], {n, 20}] PROG (PARI) lista(nn) = vector(nn, n, prod(i=1, n, sigma(i, 2))) \\ Michel Marcus, Oct 01 2014 CROSSREFS Cf. A000203 (sigma), A001157 (sigma_2), A066780 (product{i=1..n} sigma(i)), A066843, A345158, A345160. Sequence in context: A320502 A116906 A051893 * A082100 A299353 A180976 Adjacent sequences:  A247948 A247949 A247950 * A247952 A247953 A247954 KEYWORD nonn,easy AUTHOR Wesley Ivan Hurt, Oct 01 2014 STATUS approved

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Last modified July 29 22:32 EDT 2021. Contains 346346 sequences. (Running on oeis4.)