OFFSET
1,2
COMMENTS
Called "lozenge" because the Gaussian integers considered here form up a lozenge or diamond in the complex plane.
All terms are purely real integers.
FORMULA
log |a(n)| ~ 2n^2 log n. - Charles R Greathouse IV, May 01 2012
EXAMPLE
a(2) = -2 * (-1 - i) * -1 * (-1 + i) * -2i * -i * i * 2i * (1 - i) * 1 * (1 + i) * 2 = 64. (Note that numbers like -2 + i are skipped over in the computation of a(2) because abs(-2) + abs(1) > 2).
MATHEMATICA
Table[Times@@Select[ReplaceAll[Flatten[Table[a + b I, {a, -n, n}, {b, -n, n}]], 0 -> 1], Abs[Re[#]] + Abs[Im[#]] <= n&], {n, 10}]
PROG
(PARI) a(n)=(-1)^n*prod(i=1, n, prod(j=1, n-i, i^2+j^2))^2*n!^4 \\ Charles R Greathouse IV, May 01 2012
CROSSREFS
KEYWORD
sign
AUTHOR
Alonso del Arte, Jan 09 2012
STATUS
approved