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A189933

a(n) = n + [n*r/t] + [n*s/t]; r=1, s=(sin(Pi/5))^2, t=(cos(Pi/5))^2.

2, 6, 8, 12, 14, 18, 20, 24, 26, 30, 32, 36, 38, 42, 44, 48, 50, 54, 58, 60, 64, 66, 70, 72, 76, 78, 82, 84, 88, 90, 94, 96, 100, 102, 106, 110, 112, 116, 118, 122, 124, 128, 130, 134, 136, 140, 142, 146, 148, 152, 154, 158, 160, 164, 168, 170, 174, 176, 180, 182, 186, 188, 192, 194, 198, 200, 204, 206, 210, 212, 216, 220, 222, 226, 228, 232, 234, 238, 240

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OFFSET

1,1

LINKS

G. C. Greubel, Table of n, a(n) for n = 1..10000

FORMULA

From G. C. Greubel, Jan 13 2018: (Start)

A005408: a(n) = n + [n*(sin(Pi/5))^2] + [n*(cos(Pi/5))^2] = 2*n - 1.

A189932: b(n) = n + [n*(csc(Pi/5))^2] + [n*(cot(Pi/5))^2].

A189933: c(n) = n + [n*(sec(Pi/5))^2] + [n*(tan(Pi/5))^2]. (End)

MATHEMATICA

With[{s=Sin[Pi/5]^2, t=Cos[Pi/5]^2}, Table[n+Floor[n/t]+Floor[(n*s)/t], {n, 80}]] (* Harvey P. Dale, Feb 22 2013 *)