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 A004204 M3569 #31 Mar 30 2025 09:29:23 %S A004204 1,1,0,4,20,144,630,5696,39366,366400,3634950,39066624,479163828, %T A004204 6226534272,87238701000,1315130458112,20922813624336,355586138666496, %U A004204 6402373841107998,121479626301440000 %N A004204 Number of permutations of length n with spread 0. %C A004204 The spread of a permutation p is the sum of i*p(i) over 0 <= i < n, reduced modulo n. - _Rintaro Matsuo_, Nov 26 2022 %D A004204 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). %H A004204 Rintaro Matsuo, <a href="/A004204/b004204.txt">Table of n, a(n) for n = 1..40</a> %H A004204 R. L. Graham, and D. H. Lehmer, <a href="https://doi.org/10.1017/S1446788700019339">On the Permanent of Schur's Matrix</a>, Jour. Australian Math. Soc. 21 no. 4 (series A) (1976), 487-497. %H A004204 Rintaro Matsuo, <a href="https://github.com/windows-server-2003/OEIS_calculation/tree/master/contents/permutation_spread">Code used to calculate up to a(40)</a> %o A004204 (PARI) a(n) = my(v=[1..n], nb=0); forperm(v, p, if (sum(i=1, n-1, Mod(i,n)*p[i]) == 0, nb++)); nb; \\ _Michel Marcus_, Nov 30 2022 %Y A004204 Column k=0 of A147679. %K A004204 nonn %O A004204 1,4 %A A004204 _N. J. A. Sloane_ %E A004204 More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), May 17 2007