A179344 Number of permutations of 1..n with i-7<=p(i)<=i+2.

1, 2, 6, 18, 54, 162, 486, 1458, 4246, 12355, 36301, 106872, 314548, 925540, 2722708, 8007988, 23549956, 69253444, 203672180, 599025237, 1761804533, 5181627922, 15239550410, 44820508518, 131819918570, 387690809990, 1140224528970

Offset

1,2

Links

R. H. Hardin, Table of n, a(n) for n = 1..400

Formula

G.f.: -(-1 + x^2 + 2*x^3 + 4*x^4 + 7*x^5 + 12*x^6 + 17*x^7 + 6*x^8 + 28*x^9 - 4*x^10 - 4*x^11 - 2*x^12 - 6*x^13 - 4*x^15 - 8*x^16 - 2*x^17 - 10*x^18 + x^20 + x^22 + x^25 + x^27) / (1 - x - 2*x^2 - 4*x^3 - 8*x^4 - 15*x^5 - 29*x^6 - 54*x^7 - 92*x^8 - 120*x^9 + 11*x^10 + 19*x^11 + 28*x^12 + 28*x^13 + 11*x^15 + 35*x^16 + 68*x^17 + 68*x^18 - 5*x^20 - 11*x^21 - 10*x^22 - 5*x^25 - 15*x^26 - 14*x^27 + x^30 + x^31 + x^35 + x^36). - Vaclav Kotesovec, Dec 01 2012

Crossrefs

Sequence in context: A160175 A072852 A072853 * A179349 A179355 A179362

Adjacent sequences: A179341 A179342 A179343 * A179345 A179346 A179347

Keyword

nonn

Author

R. H. Hardin, Jul 11 2010

Status

approved