A342482 - OEIS

A342482

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

0, 12, 50, 150, 392, 952, 2214, 5010, 11132, 24420, 53066, 114478, 245520, 524016, 1113806, 2358954, 4980356, 10485340, 22019634, 46136838, 96468440, 201325992, 419429750, 872414530, 1811938572, 3758095572, 7784627354, 16106126430, 33285995552, 68719475680

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OFFSET

3,2

COMMENTS

a(n) is the number of ternary strings of length n with at least one 0, at least two 1's, and one 2.

LINKS

Table of n, a(n) for n=3..32.

Index entries for linear recurrences with constant coefficients, signature (7,-19,25,-16,4).

FORMULA

G.f.: 2*x^4*(6 - 17*x + 14*x^2 - 4*x^3)/((1 - x)^3*(1 - 2*x)^2). - Stefano Spezia, Mar 14 2021

EXAMPLE

a(6)=150 since the strings are the 30 permutations of 201111, the 60 permutations of 200111 and the 60 permutations of 200011.