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 A018931 #12 Sep 29 2023 21:51:57 %S A018931 0,1,2,12,72,480,3600,30240,282240,2903040,32659200,399168000, %T A018931 5269017600,74724249600,1133317785600,18307441152000,313841848320000, %U A018931 5690998849536000,108840352997376000,2189611807358976000,46225138155356160000,1021818843434188800000 %N A018931 The number of permutations of n cards in which 2 is the first card hit and 3 the next hit after 2. %C A018931 From the game of Mousetrap. %D A018931 Daniel J. Mundfrom, A problem in permutations: the game of "Mousetrap". European J. Combin. 15 (1994), no. 6, 555-560. %H A018931 D. J. Mundfrom, <a href="http://dx.doi.org/10.1006/eujc.1994.1057">A problem of permutations: the Game of "Mousetrap"</a>, Eur. J. Combinat. 15 (1994) 555-560, Table 1. %F A018931 a(n) = A062119(n-3), n > 4. - _R. J. Mathar_, Oct 02 2008 %Y A018931 Cf. A002468. %K A018931 nonn %O A018931 3,3 %A A018931 _N. J. A. Sloane_ %E A018931 Offset changed to 3 and more precise definition provided by _R. J. Mathar_, Oct 02 2008