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A308714 Decimal expansion of 2*Pi*sech(sqrt(5/3)*Pi/2)/3. 2
5, 4, 1, 9, 1, 2, 3, 2, 5, 8, 3, 2, 5, 3, 0, 1, 2, 9, 9, 4, 1, 1, 0, 2, 3, 6, 6, 2, 1, 2, 6, 5, 7, 8, 0, 0, 3, 9, 5, 0, 2, 5, 8, 8, 4, 8, 9, 2, 8, 1, 6, 2, 0, 9, 1, 4, 9, 6, 0, 6, 3, 3, 6, 0, 8, 1, 4, 6, 9, 5, 3, 7, 9, 4, 5, 6, 2, 1, 1, 4, 3, 7, 7, 6, 3, 5, 7, 5, 7, 5, 1, 9, 4, 8, 6, 8, 2, 8, 0, 7, 3, 7, 3, 2, 7, 8, 6, 7, 5, 1, 2, 3, 2, 8, 6, 3, 8, 4, 2, 2 (list; constant; graph; refs; listen; history; text; internal format)
OFFSET

0,1

LINKS

Table of n, a(n) for n=0..119.

FORMULA

Equals Product_{k>=2} (1 - 1/(3*k*(k - 1)/2 + 1)).

Equals Product_{k>=2} (1 - 1/A005448(k)).

EXAMPLE

0.5419123258325301299411023662126578003950258848928...

MATHEMATICA

RealDigits[2 Pi Sech[Sqrt[5/3] Pi/2]/3, 10, 120][[1]]

PROG

(PARI) 2*Pi*(1/cosh(sqrt(5/3)*Pi/2))/3 \\ Michel Marcus, Jun 20 2019

CROSSREFS

Cf. A005448, A308642, A308713.

Sequence in context: A258639 A072222 A197001 * A213055 A005752 A098494

Adjacent sequences:  A308711 A308712 A308713 * A308715 A308716 A308717

KEYWORD

nonn,cons

AUTHOR

Ilya Gutkovskiy, Jun 19 2019

STATUS

approved

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Last modified May 28 17:37 EDT 2020. Contains 334684 sequences. (Running on oeis4.)