# Greetings from The On-Line Encyclopedia of Integer Sequences! http://oeis.org/ Search: id:a280654 Showing 1-1 of 1 %I A280654 #17 Apr 13 2017 12:26:03 %S A280654 1,3,23,404,9524,357264,16987536,1061800704,87631559424,8894837836800, %T A280654 1063107188812800,151494084266803200,25373057708287180800, %U A280654 5011895098867920076800,1135276451701834014720000,292340783888393707192320000,84048723407048386326036480000 %N A280654 a(n) = (n!)^2 * Sum_{k=1..n} A008836(k)/k^2. %H A280654 Daniel Suteu, Table of n, a(n) for n = 1..100 %H A280654 Wikipedia, Liouville function. %F A280654 Limit_{n->infinity} a(n)/(n!)^2 = zeta(4)/zeta(2) = Pi^2/15. %t A280654 Table[(n!)^2 * Sum[(-1)^PrimeOmega[k]/k^2, {k, n}], {n, 20}] (* _Indranil Ghosh_, Apr 13 2017 *) %o A280654 (PARI) a(n) = (n!)^2 * sum(k=1,n,(-1)^bigomega(k)/k^2); %Y A280654 Cf. A001044, A008836, A182448 (Pi^2/15). %K A280654 nonn %O A280654 1,2 %A A280654 _Daniel Suteu_, Apr 12 2017 # Content is available under The OEIS End-User License Agreement: http://oeis.org/LICENSE