Entry P0015
ID: P0015
Patterns: 5 1 2 3 4
5 1 2 4 3
5 1 4 2 3
5 2 1 3 4
5 2 1 4 3
5 2 4 1 3
4 1 6 2 3 5
4 1 6 2 5 3
4 2 6 1 3 5
4 2 6 1 5 3
6 4 5 1 2 3
6 4 5 2 1 3
4 1 3 7 2 5 6
4 1 3 7 2 6 5
4 1 7 5 6 2 3
4 2 3 7 1 5 6
4 2 3 7 1 6 5
4 2 7 5 6 1 3
4 1 3 8 6 7 2 5
4 2 3 8 6 7 1 5
Title: Permutations generated by a stack of depth two and an infinite stack
References: M. Elder, Permutations generated by a stack of depth 2 and an infinite stack in series, Electron. J. Combin, 13(1) (2006), R68.
M. Elder, G. Lee, A. Rechnitzer, Permutations generated by a depth 2 and infinite stack in series are algebraic, arXiv:1407.4248, 2014.
Enumeration: ((1+q)*(1+5*q-q^2-q^3-(1-q)*sqrt((1-q^2)*(1-4*q-q^2))))/(8*q) with q = (1-2*z-sqrt(1-4*z))/(2*z)
OEIS: A245233
Contributor: Richard Stanley - August 1, 2006 & Murray Elder - March 31, 2015