A175033 Numbers n such that (ceiling(sqrt(n*n/2)))^2 - n*n/2 = 17/2.

9, 15, 55, 89, 321, 519, 1871, 3025, 10905, 17631, 63559, 102761, 370449, 598935, 2159135, 3490849, 12584361, 20346159, 73347031, 118586105, 427497825, 691170471

Offset: 1

Author

Ctibor O. Zizka, Nov 09 2009

Keywords

• nonn
• more

Comments

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.

Conjecture: a(n) = 6*a(n-2) - a(n-4). - Charles R Greathouse IV, Apr 30 2016

Crossrefs

Cf. A005319, A077444, A081554, A002315, A077446,

Programs

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

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

Extensions

More terms from Michel Marcus, Jun 02 2013

a(17)-a(22) from Charles R Greathouse IV, Apr 30 2016