OFFSET
1,1
COMMENTS
Intersection of A000384 and A193866 (even pentagonal numbers divided by 2). - Michel Marcus, Jun 20 2015
LINKS
Colin Barker, Table of n, a(n) for n = 1..251
Index entries for linear recurrences with constant coefficients, signature (9603,-9603,1).
FORMULA
G.f.: -x*(x^2+693*x+6) / ((x-1)*(x^2-9602*x+1)).
EXAMPLE
6 is in the sequence because 6 is the 2nd hexagonal number, and 2*6 is the 3rd pentagonal number.
MATHEMATICA
LinearRecurrence[{9603, -9603, 1}, {6, 58311, 559902916}, 20] (* Vincenzo Librandi, Jun 20 2015 *)
PROG
(PARI) Vec(-x*(x^2+693*x+6)/((x-1)*(x^2-9602*x+1)) + O(x^20))
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Colin Barker, Jun 19 2015
STATUS
approved