A084248 Decimal expansion of c = Product_{k>=1} (1 + 1/t(k)) where t(k) = k(k+1)/2 is the k-th triangular number.

5, 0, 7, 9, 2, 2, 0, 2, 0, 8, 6, 6, 3, 6, 7, 8, 3, 3, 6, 0, 4, 3, 6, 8, 7, 9, 5, 6, 7, 8, 2, 0, 2, 1, 0, 7, 4, 8, 3, 2, 3, 9, 7, 3, 4, 5, 7, 0, 8, 3, 5, 9, 7, 7, 4, 2, 8, 4, 8, 2, 4, 3, 7, 9, 1, 6, 8, 7, 4, 5, 9, 0, 9, 3, 2, 9, 1, 9, 9, 0, 6, 9, 4, 7, 0, 1, 5, 4, 5, 4, 9, 0, 2, 3, 3, 4, 9, 0, 3, 6, 1, 0, 2, 8, 8

Offset

1,1

References

Bruce C. Berndt, Ramanujan Notebook part II, Infinite series, Springer Verlag, 1989, p. 241.

Links

Table of n, a(n) for n=1..105.

Formula

Equals ((1/2)/Pi)*cosh(Pi/2*sqrt(7)).

Example

5.07922020866367833604368795...

Mathematica

RealDigits[Cosh[Pi/2*Sqrt[7]]/(2*Pi), 10, 120][[1]] (* Amiram Eldar, Jun 01 2023 *)

Prog

(PARI) 1/2/Pi*cosh(Pi/2*sqrt(7))

Crossrefs

Cf. A000217.

Sequence in context: A114124 A155827 A244045 * A201417 A147666 A343071

Adjacent sequences: A084245 A084246 A084247 * A084249 A084250 A084251

Keyword

cons,nonn

Author

Benoit Cloitre, Jun 21 2003

Status

approved