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A112986
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Crossing number of K_{4,n} on the real projective plane.
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0
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0, 0, 0, 3, 5, 7, 18, 22, 26, 45, 51, 57, 84, 92, 100, 135, 145, 155, 198, 210, 222, 273, 287, 301, 360, 376, 392, 459, 477, 495, 570, 590, 610, 693, 715, 737, 828, 852, 876, 975, 1001, 1027, 1134, 1162, 1190, 1305, 1335, 1365, 1488, 1520, 1552, 1683, 1717, 1751, 1890
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OFFSET
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0,4
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LINKS
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FORMULA
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a(n) = floor(n/3)*(2*n-3). [Corrected by Amiram Eldar, May 15 2024]
G.f.: -x^3*(5*x^3+2*x^2+2*x+3) / ((x-1)^3*(x^2+x+1)^2). - Colin Barker, Mar 06 2014
Sum_{n>=3} 1/a(n) = 2*log(2)/3 + 6 - sqrt(3)*Pi. - Amiram Eldar, May 15 2024
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MATHEMATICA
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a[n_] := Floor[n/3]*(2*n - 3); Array[a, 100, 0] (* Amiram Eldar, May 15 2024 *)
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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