This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A245087 #34 Jul 24 2014 11:04:55 %S A245087 0,0,1,4,22,116,716,5034,40314,362874,3628789,39916793,479001588, %T A245087 6227020788,87178291188,1307674367982,20922789887982,355687428095978, %U A245087 6402373705727977,121645100408831983,2432902008176639978,51090942171709439975,1124000727777607679972 %N A245087 Largest number such that 2^a(n) is a divisor of (n!)!. %C A245087 Also the number of trailing zeros in the binary expansion of (n!)!. %H A245087 Stanislav Sykora, <a href="/A245087/b245087.txt">Table of n, a(n) for n = 0..399</a> %F A245087 a(n) = n! - Hw(n!), Hw being the Hamming weight function. %F A245087 a(n) = A011371(A000142(n)). %e A245087 a(4)=22 because (4!)!=620448401733239439360000 is divisible by 2^22 but not by 2^23. %o A245087 (PARI) a(n) = n!-hammingweight(n!) %Y A245087 Cf. A000120 (Hamming weights), A000142, A000197, A011371. %K A245087 nonn %O A245087 0,4 %A A245087 _Stanislav Sykora_, Jul 15 2014