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A248520
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Numbers k such that floor(cot(Pi/(2k+2))) = floor(cot(Pi/(2k))).
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2
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2, 5, 8, 10, 13, 16, 19, 21, 24, 27, 30, 32, 35, 38, 41, 43, 46, 49, 52, 55, 57, 60, 63, 66, 68, 71, 74, 77, 79, 82, 85, 88, 90, 93, 96, 99, 101, 104, 107, 110, 112, 115, 118, 121, 123, 126, 129, 132, 134, 137, 140, 143, 145, 148, 151, 154, 156, 159, 162
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OFFSET
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1,1
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LINKS
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FORMULA
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EXAMPLE
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([cot(Pi/(2k+2))] = [cot(Pi/(2k))]) = (1, 0, 1, 1, 0, 1, 1, 0, 1, 0, 1, 1, 0, 1, 1, 0,...), so that A248520 = (2, 5, 8, 10, 13, 16, ...) and A248521 = (1, 3, 4, 6, 7, 9, 11, ...).
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MATHEMATICA
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z = 240; v = Table[Floor[Cot[Pi/(2 n)]], {n, 1, z}];
Flatten[Position[Differences[v], 0]] (* A248520 *)
Flatten[Position[Differences[v], 1]] (* A248521 *)
nmax=200; Select[Range[nmax], Floor[Cot[Pi/(2#+2)]]==Floor[Cot[Pi/(2#)]]&] (* Vaclav Kotesovec, Oct 09 2014 *)
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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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