OFFSET
1,1
COMMENTS
Positive integers x in the solutions to 2*x^2-176*y^2-15312*y-446600 = 0.
LINKS
Colin Barker, Table of n, a(n) for n = 1..1000
Index entries for linear recurrences with constant coefficients, signature (0,0,0,394,0,0,0,-1).
FORMULA
a(n) = 394*a(n-4)-a(n-8).
G.f.: -22*x*(11*x^7+11*x^6+101*x^5+115*x^4-2545*x^3-1789*x^2-115*x-101) / (x^8-394*x^4+1).
EXAMPLE
2222 is in the sequence because 2222^2 = 4937284 = 192^2+193^2+...+279^2.
MATHEMATICA
LinearRecurrence[{0, 0, 0, 394, 0, 0, 0, -1}, {2222, 2530, 39358, 55990, 872938, 994598, 15506810, 22059818}, 40] (* Vincenzo Librandi, May 11 2015 *)
PROG
(PARI) Vec(-22*x*(11*x^7+11*x^6+101*x^5+115*x^4-2545*x^3-1789*x^2-115*x-101) / (x^8-394*x^4+1) + O(x^100))
(Magma) I:=[2222, 2530, 39358, 55990, 872938, 994598, 15506810, 22059818]; [n le 8 select I[n] else 394*Self(n-4)-Self(n-8): n in [1..40]]; // Vincenzo Librandi, May 11 2015
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Colin Barker, May 10 2015
STATUS
approved