A116774 - OEIS

%I #8 Jul 07 2017 06:53:49

%S 1,2,6,21,69,198,498,1121,2305,4402,7910,13509,22101,34854,53250,

%T 79137,114785,162946,226918,310613,418629,556326,729906,946497,

%U 1214241,1542386,1941382,2422981,3000341,3688134

%N Number of permutations of length n which avoid the patterns 2143, 2341, 4312; or avoid the patterns 1234, 1432, 3412.

%H Lara Pudwell, <a href="http://faculty.valpo.edu/lpudwell/maple/webbook/bookmain.html">Systematic Studies in Pattern Avoidance</a>, 2005.

%H <a href="/index/Rec#order_07">Index entries for linear recurrences with constant coefficients</a>, signature (7,-21,35,-35,21,-7,1).

%F G.f.: A(x) = -{x(x^6-5x^5+13x^4-14x^3+13x^2-5x+1)}/{(x-1)^7}

%F a(n) = (n^6 - 3n^5 + 10n^4 - 15n^3 + 79n^2 - 72n + 180)/180. - Franklin T. Adams-Watters, Sep 16 2006

%K nonn,easy

%O 1,2

%A _Lara Pudwell_, Feb 26 2006