A095153 Number of 4-block covers of a labeled n-set.

35, 1225, 24990, 426650, 6779185, 104394675, 1585021340, 23909487700, 359582866335, 5400330984125, 81051093085690, 1216089331752750, 18243600636165485, 273669834496409575, 4105158293128058040, 61578149829707541800, 923677675484159636635

Offset

3,1

Links

Table of n, a(n) for n=3..19.

Index entries for linear recurrences with constant coefficients, signature (26,-196,486,-315).

Formula

a(n) = (1/4!)*(-50+35*3^n-10*7^n+15^n).

G.f.: 35*x^3*(9*x+1) / ((x-1)*(3*x-1)*(7*x-1)*(15*x-1)). - Colin Barker, Jul 13 2013

a(n) = Sum_{i=0..n} (-1)^i * C(n,i) * C(2^(n-i)-1,4). - Geoffrey Critzer, Aug 24 2014

a(n) = 26*a(n-1)-196*a(n-2)+486*a(n-3)-315*a(n-4). - Wesley Ivan Hurt, Aug 26 2014

Maple

A095153:=n->(-50+35*3^n-10*7^n+15^n)/24: seq(A095153(n), n=3..20); # Wesley Ivan Hurt, Aug 26 2014

Mathematica

nn = 19; Table[Sum[(-1)^i Binomial[n, i] Binomial[2^(n - i) - 1, 4], {i, 0, n}], {n, 3, nn}] (* Geoffrey Critzer, Aug 24 2014 *)
Table[(-50 + 35*3^n - 10*7^n + 15^n)/24, {n, 3, 20}] (* Wesley Ivan Hurt, Aug 26 2014 *)

Prog

(Magma) [(-50 + 35*3^n - 10*7^n + 15^n)/24 : n in [3..20]]; // Wesley Ivan Hurt, Aug 26 2014

Crossrefs

Column of A055154.

Sequence in context: A207722 A224175 A223867 * A223989 A224387 A224020

Adjacent sequences: A095150 A095151 A095152 * A095154 A095155 A095156

Keyword

easy,nonn

Author

Vladeta Jovovic, May 31 2004

Extensions

More terms from Colin Barker, Jul 13 2013

Status

approved