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%I #13 Apr 30 2016 03:39:39
%S 9,15,55,89,321,519,1871,3025,10905,17631,63559,102761,370449,598935,
%T 2159135,3490849,12584361,20346159,73347031,118586105,427497825,
%U 691170471
%N Numbers n such that (ceiling(sqrt(n*n/2)))^2 - n*n/2 = 17/2.
%C Let (ceiling(sqrt(n*n/2)))^2 - n*n/2 = i. Then for i=1/2 we have A002315, for i=1 we have A005319, for i=2 we have A077444, for i=7/2 we have A077446, for i=4 we have A081554.
%C Conjecture: a(n) = 6*a(n-2) - a(n-4). - _Charles R Greathouse IV_, Apr 30 2016
%o (PARI) lista(nn)=for (n=1, nn, if ((ceil(sqrt(n*n/2)))^2 - n*n/2 == 17/2, print1(n, ", "));); \\ _Michel Marcus_, Jun 02 2013
%o (PARI) forstep(n=9,1e9,2, if((sqrtint(n^2\2)+1)^2==(n^2+17)/2, print1(n", "))) \\ _Charles R Greathouse IV_, Apr 30 2016
%Y Cf. A005319, A077444, A081554, A002315, A077446,
%K nonn,more
%O 1,1
%A _Ctibor O. Zizka_, Nov 09 2009
%E More terms from _Michel Marcus_, Jun 02 2013
%E a(17)-a(22) from _Charles R Greathouse IV_, Apr 30 2016