OFFSET
1,2
COMMENTS
Bisection of A027963.
LINKS
Colin Barker, Table of n, a(n) for n = 1..1000
Index entries for linear recurrences with constant coefficients, signature (6,-13,13,-6,1).
FORMULA
From Colin Barker, Feb 19 2016: (Start)
a(n) = (-6+(2^(-1-n)*((3-sqrt(5))^n*(-25+11*sqrt(5)) + (3+sqrt(5))^n*(25+11*sqrt(5))))/sqrt(5) + 7*(1+n) - 6*(1+n)*(2+n)).
a(n) = 6*a(n-1)-13*a(n-2)+13*a(n-3)-6*a(n-4)+a(n-5) for n>5.
G.f.: x*(1+13*x-2*x^3) / ((1-x)^3*(1-3*x+x^2)).
(End)
MATHEMATICA
LinearRecurrence[{6, -13, 13, -6, 1}, {1, 19, 101, 370, 1148}, 30] (* Harvey P. Dale, Aug 19 2020 *)
PROG
(PARI) Vec(x*(1+13*x-2*x^3)/((1-x)^3*(1-3*x+x^2)) + O(x^40)) \\ Colin Barker, Feb 19 2016
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved