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 A055459 #15 Jun 02 2019 11:26:47
%S A055459 2,1,11,14,81,242,1142,4771,29009,127876,805947,4868681,31862753
%N A055459 a(n) = number of permutations of {1,...,n} which are twice but not 3-times reformable.
%C A055459 Consider a permutation {a1,...,an}; start counting from the beginning: if a1 is not 1, a1 is replaced at the end of an, until we reach the first i such that ai=i in which case ai is removed and the count start from 1 again. The permutation is unreformable if a count of n+1 is reached before all ai are removed. Otherwise, the order of removal of the ai defines the reformed permutation.
%D A055459 A. M. Bersani, "Reformed permutations in Mousetrap and its generalizations", preprint MeMoMat n. 15/2005.
%D A055459 R. K. Guy and R. J. Nowakowski, "Mousetrap," in D. Miklos, V. T. Sos and T. Szonyi, eds., Combinatorics, Paul Erdős is Eighty. Bolyai Society Math. Studies, Vol. 1, pp. 193-206, 1993.
%H A055459 A. M. Bersani, <a href="http://www.dmmm.uniroma1.it/~alberto.bersani/mousetrap.html">On the game Mousetrap</a>.
%H A055459 R. K. Guy and R. J. Nowakowski, <a href="https://www.jstor.org/stable/2975171">Mousetrap</a> Amer. Math. Monthly, 101 (1994), 1007-1010.
%e A055459 a(4)=2 since 4213->2134->3214, 1432->1423->1234 are the only two permutations that can be reformed twice.
%Y A055459 Cf. A007709, A007711, A007712, A067950.
%K A055459 nonn
%O A055459 1,1
%A A055459 _Robert G. Wilson v_, Jul 05 2000
%E A055459 Edited by Kok Seng Chua (chuaks(AT)ihpc.nus.edu.sg), Mar 06 2002
%E A055459 2 more terms from Alberto M. Bersani (bersani(AT)dmmm.uniroma1.it), Feb 07 2007
%E A055459 One more term from Alberto M. Bersani (bersani(AT)dmmm.uniroma1.it), Feb 24 2008