A179349 Number of permutations of 1..n with i-8<=p(i)<=i+2.

1, 2, 6, 18, 54, 162, 486, 1458, 4374, 12866, 37831, 111961, 331804, 983200, 2913064, 8629984, 25563928, 75720112, 224270920, 664246912, 1967449976, 5827579985, 17261274041, 51127661518, 151439081294, 448558789858, 1328619061294

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 - 8*x^5 - 14*x^6 - 24*x^7 - 34*x^8 - 12*x^9 - 56*x^10 + 11*x^11 + 16*x^12 + 19*x^13 + 12*x^14 + 28*x^15 + 8*x^17 + 16*x^18 + 4*x^19 + 20*x^20 - 5*x^22 - 8*x^23 - 3*x^24 - 10*x^25 - 2*x^28 - 2*x^30 + x^33 + x^35) / (-1 + x + 2*x^2 + 4*x^3 + 8*x^4 + 16*x^5 + 30*x^6 + 58*x^7 + 108*x^8 + 184*x^9 + 240*x^10 - 26*x^11 - 48*x^12 - 82*x^13 - 120*x^14 - 120*x^15 - 22*x^17 - 70*x^18 - 136*x^19 - 136*x^20 + 16*x^22 + 46*x^23 + 78*x^24 + 68*x^25 + 10*x^28 + 30*x^29 + 28*x^30 - 6*x^33 - 16*x^34 - 14*x^35 - 2*x^39 - 2*x^40 + x^44 + x^45). - Vaclav Kotesovec, Dec 01 2012

Crossrefs

Sequence in context: A072852 A072853 A179344 * A179355 A179362 A008776

Adjacent sequences: A179346 A179347 A179348 * A179350 A179351 A179352

Keyword

nonn

Author

R. H. Hardin, Jul 11 2010

Status

approved