%I A082291
%S A082291 2,19,118,695,4058,23659,137902,803759,4684658,27304195,159140518,
%T A082291 927538919,5406093002,31509019099,183648021598,1070379110495,
%U A082291 6238626641378,36361380737779,211929657785302,1235216565974039
%N A082291 Expansion of x(2+5x-x^2)/((1-x)(1-6x+x^2)).
%C A082291 Integers n such that (n+1)^2+(n+2)^2 is a square.
%H A082291 <a href="Sindx_Tu.html#2wis">Index entries for two-way infinite sequences</
               a>
%F A082291 G.f.: x(2+5x-x^2)/((1-x)(1-6x+x^2)). a(n)=6a(n-1)-a(n-2)+6. a(-1-n)=-3-a(n).
%F A082291 A001109(n+1)+A001109(n)=2a(n)+3, a(n+1)=7a(n)-4*A001109(n)+9. - Klaus 
               Strassburger (strass(AT)ddfi.uni-duesseldorf.de)
%o A082291 (PARI) a(n)=if(n<0,-3-a(-1-n),if(n==0,-1,polcoeff(x*(2+5*x-x^2)/((1-x)*(1-6*x+x^2))+x*O(x^n),
               n)))
%o A082291 (PARI) {a(n)=subst(poltchebi(n+1)-poltchebi(n)-6, x, 3)/4}
%Y A082291 Cf. A001652(n)=a(n)+1.
%Y A082291 Sequence in context: A055875 A089659 A101253 this_sequence A055518 A089364 
               A166298
%Y A082291 Adjacent sequences: A082288 A082289 A082290 this_sequence A082292 A082293 
               A082294
%K A082291 nonn,easy
%O A082291 1,1
%A A082291 Michael Somos, Apr 07 2003