login
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.
2
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.
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
KEYWORD
cons,nonn
AUTHOR
Benoit Cloitre, Jun 21 2003
STATUS
approved