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A196787 a(n) = 3*a(n-1) - 2*a(n-2) - a(n-4) + a(n-5) with initial terms 1, 1, 1, 3, 6. 2
1, 1, 1, 3, 6, 12, 24, 46, 87, 163, 303, 561, 1036, 1910, 3518, 6476, 11917, 21925, 40333, 74191, 136466, 251008, 461684, 849178, 1561891, 2872775, 5283867, 9718557, 17875224, 32877674, 60471482, 111224408, 204573593, 376269513, 692067545 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

LINKS

Table of n, a(n) for n=1..35.

Index entries for linear recurrences with constant coefficients, signature (3,-2,0,-1,1).

FORMULA

a(1)=1, a(2)=1, a(3)=1; a(n) = a(n-1) + a(n-2) + a(n-3) + n - 4 for n >= 4.

G.f.: x*(-1+2*x-2*x^3) / ((x-1)^2*(x^3+x^2+x-1)).

EXAMPLE

a(7) = (a(6): 12) + (a(5): 6) + (a(4): 3) + (n-4: 3) = 24.

MATHEMATICA

LinearRecurrence[{3, -2, 0, -1, 1}, {1, 1, 1, 3, 6}, 42] (* T. D. Noe, Oct 06 2011 *)

PROG

(PARI) x='x+O('x^43); Vec(x*(-1+2*x-2*x^3) / ((x-1)^2*(x^3+x^2+x-1))) \\ Georg Fischer, Apr 03 2019

CROSSREFS

Sequence in context: A132979 A163314 A018183 * A200662 A264507 A137711

Adjacent sequences:  A196784 A196785 A196786 * A196788 A196789 A196790

KEYWORD

nonn,easy

AUTHOR

Aditya Subramanian, Oct 06 2011

EXTENSIONS

Better name from Charles R Greathouse IV, Oct 06 2011

Edited and corrected by Georg Fischer, Apr 03 2019

STATUS

approved

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Last modified January 18 00:33 EST 2022. Contains 350410 sequences. (Running on oeis4.)