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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 + "<br>");

}

(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.)