Search: id:A055459 Results 1-1 of 1 results found. %I A055459 %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 Erdos is Eighty. Bolyai Society Math. Studies, Vol. 1, pp. 193-206, 1993. %D A055459 R. K. Guy and R. J. Nowakowski, ``Mousetrap,'' Amer. Math. Monthly, 101 (1994), 1007-1010. %H A055459 A. M. Bersani, On the game Mousetrap. %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. %Y A055459 Sequence in context: A088587 A158352 A158354 this_sequence A080958 A138351 A120293 %Y A055459 Adjacent sequences: A055456 A055457 A055458 this_sequence A055460 A055461 A055462 %K A055459 nonn %O A055459 1,1 %A A055459 Robert G. Wilson v (rgwv(AT)rgwv.com), 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 Search completed in 0.001 seconds