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 A222639 #14 Jul 14 2020 07:40:45 %S A222639 1,1,1,4,1,1,1,10,1,1,1,2,13,1,1,2,1,1,1,20,1,1,1,58,1,1,1,2,1,1,1,2, %T A222639 5,1,1,4,1,1,1,2,1,1,1,2,5,1,1,2,1,1,1,8,1,1,1,2,1,5,1,2,1,1,1,2,23,1, %U A222639 1,4,1,5,1,2,1,37 %N A222639 Square root of the square part of the total number of arrangements of a set with n elements. %H A222639 F. Luca and I. E. Shparlinski, <a href="https://doi.org/10.1017/S0017089507003734">On the squarefree parts of floor(e*n!)</a>, Glasgow Math. J., 49 (2007), 391-403. %F A222639 a(n) = sqrt(A000522(n)/core(A000522(n))). %o A222639 (PARI) a(n) = core(n! * polcoeff(exp(x + x*O(x^n)) / (1 - x), n), 1)[2] %Y A222639 Cf. A000188, A000522, A007913, A222637. %K A222639 nonn %O A222639 0,4 %A A222639 _Michel Marcus_, Feb 27 2013