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 A331757 Number of edges in a figure made up of a row of n adjacent congruent rectangles upon drawing diagonals of all possible rectangles. 12
 8, 28, 80, 178, 372, 654, 1124, 1782, 2724, 3914, 5580, 7626, 10352, 13590, 17540, 22210, 28040, 34670, 42760, 51962, 62612, 74494, 88508, 104042, 121912, 141534, 163664, 187942, 215636, 245490, 279260, 316022, 356456, 399898, 447612, 498698, 555352 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS FORMULA a(n) = 2*n + 2 + 3*A324042(n) + 4*A324043(n). MATHEMATICA Table[n^2 + 4n + 1 + Sum[Sum[(2 * Boole[GCD[i, j] == 1] - Boole[GCD[i, j] == 2]) * (n + 1 - i) * (n + 1 - j), {j, 1, n}], {i, 1, n}], {n, 1, 37}] (* Joshua Oliver, Feb 05 2020 *) CROSSREFS A306302 gives number of regions in the figure. This is column 1 of A331454. Cf. A324042, A324043. Sequence in context: A134638 A293289 A305638 * A130129 A317032 A229713 Adjacent sequences:  A331754 A331755 A331756 * A331758 A331759 A331760 KEYWORD nonn AUTHOR N. J. A. Sloane, Feb 04 2020 STATUS approved

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Last modified August 3 05:55 EDT 2020. Contains 336197 sequences. (Running on oeis4.)