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A036542
a(n) = T(n, n), array T given by A047858.
1
1, 3, 11, 34, 93, 236, 571, 1338, 3065, 6904, 15351, 33782, 73717, 159732, 344051, 737266, 1572849, 3342320, 7077871, 14942190, 31457261, 66060268, 138412011, 289406954, 603979753, 1258291176, 2617245671, 5435817958, 11274289125, 23353884644, 48318382051
OFFSET
0,2
FORMULA
a(n) = 3*n * 2^(n-1) - n + 1.
From Colin Barker, Feb 20 2016: (Start)
a(n) = 6*a(n-1)-13*a(n-2)+12*a(n-3)-4*a(n-4) for n>3.
G.f.: (1-3*x+6*x^2-5*x^3) / ((1-x)^2*(1-2*x)^2).
(End)
MATHEMATICA
LinearRecurrence[{6, -13, 12, -4}, {1, 3, 11, 34}, 40] (* Harvey P. Dale, Jul 21 2024 *)
PROG
(PARI) Vec((1-3*x+6*x^2-5*x^3)/((1-x)^2*(1-2*x)^2) + O(x^40)) \\ Colin Barker, Feb 20 2016
CROSSREFS
Sequence in context: A018413 A004662 A247103 * A084266 A357592 A052471
KEYWORD
nonn,easy
STATUS
approved