OFFSET
1,2
COMMENTS
Odd positive integers C such that 27*C^2 - 4 = 23*D^2, where D is integer.
LINKS
Colin Barker, Table of n, a(n) for n = 1..450
William C. Jagy, following Irving Kaplansky, 2009. Integers not represented by 2x^2 + xy + 3y^2 + z^3 - z
William C. Jagy, Integers not represented by x^2 + xy + 3y^2 + z^3 - z, MathOverflow.
Index entries for linear recurrences with constant coefficients, signature (0,15550,0,-1).
FORMULA
For n>4, a(n) = 15550*a(n-2) - a(n-4).
G.f.: x*(1 - x)*(1 + 600*x + x^2) / (1 - 15550*x^2 + x^4). - Colin Barker, Mar 31 2018
PROG
(PARI) Vec(x*(1 - x)*(1 + 600*x + x^2) / (1 - 15550*x^2 + x^4) + O(x^20)) \\ Colin Barker, Mar 31 2018
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Artur Jasinski, Jan 29 2010
EXTENSIONS
More terms from Max Alekseyev, Dec 15 2013
STATUS
approved