OFFSET
1,2
COMMENTS
Also positive integers y in the solutions to 5*x^2 - 6*y^2 - 3*x + 6*y - 2 = 0, the corresponding values of x being A254964.
LINKS
Colin Barker, Table of n, a(n) for n = 1..1000
Index entries for linear recurrences with constant coefficients, signature (1,22,-22,-1,1).
FORMULA
a(n) = a(n-1)+22*a(n-2)-22*a(n-3)-a(n-4)+a(n-5).
G.f.: x*(x^3+11*x^2-x-1) / ((x-1)*(x^4-22*x^2+1)).
EXAMPLE
13 is in the sequence because the 13th centered hexagonal number is 469, which is also the 14th heptagonal number.
PROG
(PARI) Vec(x*(x^3+11*x^2-x-1)/((x-1)*(x^4-22*x^2+1)) + O(x^100))
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Colin Barker, Feb 11 2015
STATUS
approved