A294769 Number of permutations of [n] avoiding {2143, 1423, 1234}.

1, 1, 2, 6, 21, 74, 259, 905, 3163, 11058, 38664, 135193, 472724, 1652965, 5779907, 20210571, 70670238, 247112450, 864077593, 3021418466, 10564988371, 36942575637, 129177037563, 451693114846, 1579434503132, 5522805791005, 19311585094940, 67526784937389, 236120787686511

Offset

0,3

Links

Table of n, a(n) for n=0..28.

D. Callan, T. Mansour, Enumeration of small Wilf classes avoiding 1324 and two other 4-letter patterns, arXiv:1705.00933 [math.CO] (2017), Table 2 No 141.

Maple

(2*x^4-4*x^3+7*x^2-5*x+1)/(4*x^4-9*x^3+11*x^2-6*x+1) ;
taylor(%, x=0, 40) ;
gfun[seriestolist](%) ;

Crossrefs

Sequence in context: A116790 A116817 A116764 * A116738 A360151 A150186

Adjacent sequences: A294766 A294767 A294768 * A294770 A294771 A294772

Keyword

nonn,easy

Author

R. J. Mathar, Nov 08 2017

Status

approved