A079980 - OEIS

The OEIS is supported by the many generous donors to the OEIS Foundation.

A079980

Number of permutations of length 2n satisfying -k<=p(i)-i<=r and p(i)-i not in I, i=1..2n, with k=3, r=3, I={-2,0,1,2}. There is no one such permutation of length 2n+1.

1, 0, 1, 2, 3, 8, 12, 27, 52, 95, 196, 369, 720, 1408, 2709, 5292, 10249, 19894, 38675, 74992, 145692, 282823, 549000, 1066095, 2069496, 4018065, 7801024, 15144960, 29404281, 57086680, 110832225, 215178138, 417759539, 811069560, 1574664364

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,4

LINKS

Table of n, a(n) for n=0..34.

Vladimir Baltic, On the number of certain types of strongly restricted permutations, Applicable Analysis and Discrete Mathematics Vol. 4, No 1 (2010), 119-135.

Index entries for linear recurrences with constant coefficients, signature (0,1,4,2,2,-2,1,0,1).

FORMULA

Recurrence: a(n) = a(n-2)+4*a(n-3)+2*a(n-4)+2*a(n-5)-2*a(n-6)+a(n-7)+a(n-9).

G.f.: -(x^6-2*x^3+1)/(x^9+x^7-2*x^6+2*x^5+2*x^4+4*x^3+x^2-1).

CROSSREFS

Subsequence of A079981.