A308642 Decimal expansion of cosh(sqrt(13/3)*Pi/2)*sech(sqrt(5/3)*Pi/2).

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

Offset: 1

Author

Ilya Gutkovskiy, Jun 15 2019

Keywords

• nonn
• cons
• changed

Examples

			3.4084379526884991250972568943042066986209221843076631...
		

Links

• Kelvin Voskuijl, Table of n, a(n) for n = 1..20000

Crossrefs

Cf. A005448, A084248, A308666.

Programs

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]]

Formula

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

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