A291064 a(n) = 2^n*(n + 1) - 3*(n - 1).

4, 9, 26, 71, 180, 433, 1006, 2283, 5096, 11237, 24546, 53215, 114652, 245721, 524246, 1114067, 2359248, 4980685, 10485706, 22020039, 46137284, 96468929, 201326526, 419430331, 872415160, 1811939253, 3758096306, 7784628143, 16106127276, 33285996457

Offset

1,1

Comments

For n > 1, also the number of maximal irredundant sets in the n-book graph.

Links

Table of n, a(n) for n=1..30.

Eric Weisstein's World of Mathematics, Book Graph

Eric Weisstein's World of Mathematics, Maximal Irredundant Set

Index entries for linear recurrences with constant coefficients, signature (6, -13, 12, -4).

Formula

a(n) = 2^n*(n + 1) - 3*(n - 1).

a(n) = 6*a(n-1) - 13*a(n-2) + 12*a(n-3) - 4*a(n-4).

G.f.: (x (4 - 15 x + 24 x^2 - 16 x^3))/(1 - 3 x + 2 x^2)^2.

Mathematica

Table[2^n (n + 1) - 3 (n - 1), {n, 20}]
LinearRecurrence[{6, -13, 12, -4}, {4, 9, 26, 71, 180}, 20]
CoefficientList[Series[(4 - 15 x + 24 x^2 - 16 x^3)/(1 - 3 x + 2 x^2)^2, {x, 0, 20}], x]

Crossrefs

Sequence in context: A328657 A335983 A113682 * A145855 A363448 A373719

Adjacent sequences: A291061 A291062 A291063 * A291065 A291066 A291067

Keyword

nonn,easy

Author

Eric W. Weisstein, Aug 17 2017

Status

approved