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 A234459 Real part of the product of all the integer complex numbers in the square [1,1] to [n,n]. 4
 1, -20, 7800, 530400000, 2787453552000000, -7066368691421644800000000, 3108366378804858902744832000000000000, 1291087724942273632600239979303403520000000000000000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Andrew Howroyd, Table of n, a(n) for n = 1..27 EXAMPLE For n = 2, we have (1 + i)(1 + 2i)(2 + i)(2 + 2i) which gives -20 + 0i, so a(2) = -20. MATHEMATICA Table[Re[Times@@Flatten[Table[a + b I, {a, n}, {b, n}]]], {n, 20}] (* Alonso del Arte, Feb 04 2014 *) PROG (JavaScript) function cNumber(x, y) { return [x, y]; } function cMult(a, b) { return [a[0] * b[0] - a[1] * b[1], a[0] * b[1] + a[1] * b[0]]; } for (i = 1; i < 10; i++) { c = cNumber(1, 0); for (j = 1; j <= i; j++) for (k = 1; k <= i; k++) c = cMult(c, cNumber(j, k)); document.write(c + "
"); } (PARI) a(n) = real(prod(i=1, n, prod(j=1, n, i+I*j))); \\ Michel Marcus, Dec 27 2013 CROSSREFS Cf. A000142, A234460. Sequence in context: A222721 A223051 A222744 * A013725 A293286 A250021 Adjacent sequences:  A234456 A234457 A234458 * A234460 A234461 A234462 KEYWORD sign AUTHOR Jon Perry, Dec 26 2013 STATUS approved

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Last modified October 20 18:08 EDT 2018. Contains 316401 sequences. (Running on oeis4.)