NE to SW Diagonal of Ulam Spiral, with 101 at center
The sequence does not match the definition. A working definition might be a(2n)=4n^2-10n+107, a(2n-1)=4n^2+2n+101, a(n)=n^2-n+105+2*(-1)^n*(1-2*n), but this seems to be unrelated to Ulam spirals. [From R. J. Mathar, Jun 11 2009]
