OFFSET
0,2
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (2,3).
FORMULA
G.f.: (1+5*x)/((1-3*x)(1+x)).
E.g.f. 2*exp(3*x)-exp(-x).
a(0)=1, a(1)=7, a(n)=2*a(n-1)+3*a(n-2) [ Harvey P. Dale, May 24 2011]
MATHEMATICA
Total/@Partition[Riffle[2*3^Range[0, 30], {-1, 1}], 2] (* or *) LinearRecurrence[{2, 3}, {1, 7}, 30] (* Harvey P. Dale, May 24 2011 *)
CoefficientList[Series[(1 + 5 x) / ((1 - 3 x) (1 + x)), {x, 0, 40}], x] (* Vincenzo Librandi, Aug 10 2013 *)
PROG
(Magma) [2*3^n-(-1)^n: n in [0..40]]; // Vincenzo Librandi, Aug 10 2013
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Mar 26 2003
STATUS
approved