OFFSET
1,2
LINKS
Colin Barker, Table of n, a(n) for n = 1..1000
Index entries for linear recurrences with constant coefficients, signature (5,-9,7,-2).
FORMULA
Binomial transform of [1, 7, 13, 15, 15, 15, ...].
G.f. x*(1+3*x-3*x^2+x^3) / ( (2*x-1)*(x-1)^3 ). - R. J. Mathar, Apr 04 2012
From Colin Barker, Nov 04 2017: (Start)
a(n) = -8 + 15*2^(n-1) - 5*n - n^2.
a(n) = 5*a(n-1) - 9*a(n-2) + 7*a(n-3) - 2*a(n-4) for n>4.
(End)
EXAMPLE
a(3) = 28 = sum of row 3 terms of triangle A134637: 10 + 8 + 10.
a(3) = 28 = (1, 2, 1) dot (1, 8, 28) = (1 + 14 + 13).
MATHEMATICA
LinearRecurrence[{5, -9, 7, -2}, {1, 8, 28, 76}, 40] (* Harvey P. Dale, Feb 24 2018 *)
PROG
(PARI) Vec(x*(1 + 3*x - 3*x^2 + x^3) / ((1 - x)^3*(1 - 2*x)) + O(x^40)) \\ Colin Barker, Nov 04 2017
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Gary W. Adamson, Nov 04 2007
EXTENSIONS
Corrected by R. J. Mathar, Apr 04 2012
STATUS
approved