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A308642 Decimal expansion of cosh(sqrt(13/3)*Pi/2)*sech(sqrt(5/3)*Pi/2). 3
3, 4, 0, 8, 4, 3, 7, 9, 5, 2, 6, 8, 8, 4, 9, 9, 1, 2, 5, 0, 9, 7, 2, 5, 6, 8, 9, 4, 3, 0, 4, 2, 0, 6, 6, 9, 8, 6, 2, 0, 9, 2, 2, 1, 8, 4, 3, 0, 7, 6, 6, 3, 1, 2, 3, 8, 2, 7, 0, 0, 2, 6, 5, 5, 8, 4, 4, 2, 5, 0, 1, 9, 9, 6, 3, 5, 8, 9, 0, 8, 0, 0, 9, 0, 2, 8, 6, 4, 3, 4, 2, 5, 3, 3, 9, 6, 0, 0, 1, 5, 7, 2, 4, 1, 2, 2, 2, 2, 5, 6, 0, 1, 4, 0, 6, 7, 8, 3, 9, 7 (list; constant; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..120.

FORMULA

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

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

EXAMPLE

3.4084379526884991250972568943042066986209221843076631...

MATHEMATICA

RealDigits[Cosh[Sqrt[13/3] Pi/2] Sech[Sqrt[5/3] Pi/2], 10, 120][[1]]

RealDigits[Product[(1 + 1/(3 k (k - 1)/2 + 1)), {k, 1, Infinity}], 10, 120][[1]]

CROSSREFS

Cf. A005448, A084248, A308666.

Sequence in context: A214024 A215079 A049251 * A158674 A213280 A056862

Adjacent sequences:  A308639 A308640 A308641 * A308643 A308644 A308645

KEYWORD

nonn,cons

AUTHOR

Ilya Gutkovskiy, Jun 15 2019

STATUS

approved

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Last modified April 6 11:02 EDT 2020. Contains 333273 sequences. (Running on oeis4.)