A220948 Expansion of (1-x)^2*(1-3*x)/(1-9*x+28*x^2-35*x^3+15*x^4-x^5).

1, 4, 15, 55, 200, 726, 2638, 9604, 35037, 128061, 468809, 1718446, 6305546, 23155863, 85089015, 312823200, 1150506841, 4232595095, 15574796945, 57320990295, 210990647105, 776707569176, 2859475304889, 10527898398268, 38763003252400, 142727886900676, 525547912974105

Offset

0,2

Comments

A diagonal of the square array A223968.

Links

Table of n, a(n) for n=0..26.

Index entries for linear recurrences with constant coefficients, signature (9,-28,35,-15,1).

Formula

a(n) = A223968(n+2,n).

G.f.: (1-x)^2*(1-3*x)/(1-9*x+28*x^2-35*x^3+15*x^4-x^5).

a(n) = 9*a(n-1) - 28*a(n-2) + 35*a(n-3) - 15*a(n-4) + a(n-5) with a(0) = 1, a(1) = 4, a(2) = 15, a(3) = 55, a(4) = 200.

Crossrefs

Cf. A223968

Sequence in context: A126932 A094833 A039717 * A026013 A371820 A050183

Adjacent sequences: A220945 A220946 A220947 * A220949 A220950 A220951

Keyword

nonn,easy

Author

Philippe Deléham, Apr 07 2013

Status

approved