A294702 Number of permutations of [n] avoiding {1324, 2143, 3412}.

1, 1, 2, 6, 21, 71, 222, 648, 1797, 4807, 12548, 32236, 82009, 207529, 524060, 1323540, 3348087, 8491157, 21600888, 55131630, 141172311, 362617861, 934098062, 2412413026, 6244420411, 16195018711, 42072199862, 109451155098, 285073305417, 743218623827, 1939213856418, 5063148655716

Offset

0,3

Links

Table of n, a(n) for n=0..31.

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 35.

Maple

p := 1-9*x+33*x^2-62*x^3+64*x^4-38*x^5+10*x^6 ;
q := (1-3*x+x^2)*(1-2*x)^2*(1-x)^3 ;
taylor(p/q, x=0, 40) ;
gfun[seriestolist](%) ;
# alternative
A294702 := proc(n)
    2*A001519(n)+2^n*(n-6)+(n+5)*(n+2)/2 ;
end proc:
seq(A294702(n), n=0..10) ; # R. J. Mathar, Mar 21 2021

Crossrefs

Sequence in context: A116792 A116761 A116807 * A116785 A116801 A148486

Adjacent sequences: A294699 A294700 A294701 * A294703 A294704 A294705

Keyword

nonn,easy

Author

R. J. Mathar, Nov 07 2017

Status

approved