OFFSET
0,2
COMMENTS
The next terms appear to be 243453384, 849982464, 16388911447 (confirmed by Pierre CAMI).
LINKS
Index entries for linear recurrences with constant coefficients, signature (1,0,1298,-1298,0,-1,1).
FORMULA
a(0)=0, a(1)=7, a(2)=144, a(3)=504, a(4)=9727, a(6)=187560 and then a(n) = 1298*a(n-3)+648-a(n-6). - Pierre CAMI, Apr 05 2005
G.f.: x*(7+137*x+360*x^2+137*x^3+7*x^4)/((1-x)*(1-11*x+x^2)*(1+11*x+120*x^2+11*x^3+x^4)). - Bruno Berselli, Feb 19 2013
a(n) = a(n-1)+1298*a(n-3)-1298*a(n-4)-a(n-6)+a(n-7). - Bruno Berselli, Feb 19 2013
MATHEMATICA
LinearRecurrence[{1, 0, 1298, -1298, 0, -1, 1}, {0, 7, 144, 504, 9727, 187560, 654840}, 20] (* Bruno Berselli, Feb 19 2013 *)
PROG
(PARI) for(n=0, 12626287, if(issquare(13*n*(n+1)+1), print1(n, ", ")))
(Magma)
m:=19; R<x>:=PowerSeriesRing(Integers(), m); [0] cat Coefficients(R!((7+137*x+360*x^2+137*x^3+7*x^4)/((1-x)*(1-11*x+x^2)*(1+11*x+120*x^2+11*x^3+x^4)))); // Bruno Berselli, Feb 19 2013
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Gerald McGarvey, Apr 02 2005
EXTENSIONS
More terms from Pierre CAMI, Apr 05 2005
STATUS
approved