A294703 Number of permutations of [n] avoiding {1324, 2341, 4123}.

1, 1, 2, 6, 21, 72, 230, 701, 2113, 6475, 20468, 66969, 226027, 782276, 2760094, 9880455, 35758457, 130507165, 479487736, 1771213935, 6572533275, 24484124014, 91520352034, 343139355270, 1290071981495, 4862298799421, 18368091363064, 69535094533135, 263751173112167

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 1 No 49.

Formula

a(n) = A000108(n) -3*n^3/8 +3*n^2/2 -17*n/15 +3 +n^5/120 +2^(n-1)*(n-4), n>0. - R. J. Mathar, Mar 21 2021

Maple

C := (1-sqrt(1-4*x))/2/x ;
p := x^3-3*x^4+3*x^5-5*x^6+9*x^7-4*x^8 ;
q := (1-x)^6*(1-2*x)^2 ;
taylor(C+p/q, x=0, 40) ;
gfun[seriestolist](%) ;

Crossrefs

Sequence in context: A116830 A116747 A116810 * A116800 A116758 A116838

Adjacent sequences: A294700 A294701 A294702 * A294704 A294705 A294706

Keyword

nonn,easy

Author

R. J. Mathar, Nov 07 2017

Status

approved