A179355 - OEIS

%I #8 Dec 01 2012 17:03:46

%S 1,2,6,18,54,162,486,1458,4374,13122,38854,115027,342013,1017864,

%T 3029092,9013876,26821828,79807684,237456052,706492756,2101954468,

%U 6253701604,18606251668,55358626421,164706941845,490047239090,1458020343786

%N Number of permutations of 1..n with i-9<=p(i)<=i+2.

%H R. H. Hardin, <a href="/A179355/b179355.txt">Table of n, a(n) for n = 1..400</a>

%F G.f.: -(1- x^2 - 2*x^3 - 4*x^4 - 8*x^5 - 15*x^6 - 28*x^7 - 49*x^8 - 70*x^9 - 28*x^10 - 120*x^11 + 11*x^12 + 16*x^13 + 19*x^14 + 12*x^15 + 28*x^16 + 11*x^18 + 32*x^19 + 51*x^20 + 20*x^21 + 68*x^22 - 5*x^24 - 8*x^25 - 3*x^26 - 10*x^27 - 5*x^30 - 12*x^31 - 3*x^32 - 14*x^33 + x^36 + x^38 + x^42 + x^44) / (-1 + x + 2*x^2 + 4*x^3 + 8*x^4 + 16*x^5 + 31*x^6 + 61*x^7 + 118*x^8 + 220*x^9 + 376*x^10 + 496*x^11 - 26*x^12 - 48*x^13 - 82*x^14 - 120*x^15 - 120*x^16 - 26*x^18 - 92*x^19 - 222*x^20 - 392*x^21 - 392*x^22 + 16*x^24 + 46*x^25 + 78*x^26 + 68*x^27 + 16*x^30 + 66*x^31 + 138*x^32 + 124*x^33 - 6*x^36 - 16*x^37 - 14*x^38 - 6*x^42 - 20*x^43 - 18*x^44 + x^48 + x^49 + x^54 + x^55). - _Vaclav Kotesovec_, Dec 01 2012

%K nonn

%O 1,2

%A _R. H. Hardin_, Jul 11 2010