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%I #20 Jul 16 2022 11:55:09
%S 1,4,19,145,954,11952,101664,1573344,21179232,390661056,4857760512,
%T 138055228416,1989835352064,48554918608896,1184490930438144,
%U 37179368055373824,683493250562260992,26913000032107757568,548273767789158727680,23227773590084738088960,751700319286194622955520
%N a(n) = Product_{i=1..n} sigma(i) * Sum_{i=1..n} 1/sigma(i).
%H Michael De Vlieger, <a href="/A067577/b067577.txt">Table of n, a(n) for n = 1..419</a>
%t Array[Product[DivisorSigma[1, i], {i, #}]*Sum[1/DivisorSigma[1, j], {j, #}] &, 21] (* _Michael De Vlieger_, Jul 16 2022 *)
%o (PARI) a(n) = prod(i=1, n, sigma(i)) * sum(i=1, n, 1/sigma(i)); \\ _Michel Marcus_, Jan 09 2021
%Y Cf. A000203 (sigma), A066780, A212717, A212718.
%K nonn
%O 1,2
%A _Benoit Cloitre_, Jan 30 2002
%E More terms from _Michel Marcus_, Jan 09 2021
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