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%I #18 Aug 02 2018 15:19:36
%S 1,-20,7800,530400000,2787453552000000,-7066368691421644800000000,
%T 3108366378804858902744832000000000000,
%U 1291087724942273632600239979303403520000000000000000
%N Real part of the product of all the integer complex numbers in the square [1,1] to [n,n].
%H Andrew Howroyd, <a href="/A234459/b234459.txt">Table of n, a(n) for n = 1..27</a>
%e For n = 2, we have (1 + i)(1 + 2i)(2 + i)(2 + 2i) which gives -20 + 0i, so a(2) = -20.
%t Table[Re[Times@@Flatten[Table[a + b I, {a, n}, {b, n}]]], {n, 20}] (* _Alonso del Arte_, Feb 04 2014 *)
%o (JavaScript)
%o function cNumber(x, y) {
%o return [x, y];
%o }
%o function cMult(a, b) {
%o return [a[0] * b[0] - a[1] * b[1], a[0] * b[1] + a[1] * b[0]];
%o }
%o for (i = 1; i < 10; i++) {
%o c = cNumber(1, 0);
%o for (j = 1; j <= i; j++)
%o for (k = 1; k <= i; k++)
%o c = cMult(c, cNumber(j, k));
%o document.write(c + "<br>");
%o }
%o (PARI) a(n) = real(prod(i=1, n, prod(j=1, n, i+I*j))); \\ _Michel Marcus_, Dec 27 2013
%Y Cf. A000142, A234460.
%K sign
%O 1,2
%A _Jon Perry_, Dec 26 2013
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