OFFSET
1,1
LINKS
Colin Barker, Table of n, a(n) for n = 1..109
Index entries for linear recurrences with constant coefficients, signature (1536796803,-1536796803,1).
FORMULA
G.f.: -189*x*(x^2+1372105*x+34) / ((x-1)*(x^2-1536796802*x+1)).
EXAMPLE
6426 is in the sequence because 6426 is the 51st heptagonal number, and 2*6426 is the 72nd heptagonal number.
MATHEMATICA
LinearRecurrence[{1536796803, -1536796803, 1}, {6426, 9875715583923, 15176968126834688342280}, 20] (* Harvey P. Dale, May 17 2018 *)
PROG
(PARI) Vec(-189*x*(x^2+1372105*x+34)/((x-1)*(x^2-1536796802*x+1)) + O(x^20))
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Colin Barker, Jun 18 2015
STATUS
approved