A390459 Decimal expansion of Product_{k>=1} tanh(arctan(k) * arcsinh(k) / 2).

0, 8, 4, 4, 3, 9, 6, 8, 4, 0, 3, 0, 1, 8, 9

Offset

0,2

Comments

Problem 8 by Fee and Monagan (1997) was to calculate this constant to 14 significant digits.

Links

Table of n, a(n) for n=0..14.

Gregory J. Fee and Michael B. Monagan, Problem 8, Problems, Puzzles, Challenges, ACM SIGSAM Bulletin, Vol. 31, No. 1 (1997), p. 23.

Philippe Flajolet and Bruno Salvy, The SIGSAM challenges: Symbolic asymptotics in practice, ACM SIGSAM Bulletin, Vol. 31, No .4 (1997), pp. 36-47. See pp. 44-47; RT-0209, INRIA, HAL open science; author's copy.

Example

0.084439684030189...

Maple

# See Flajolet and Salvy link.

Crossrefs

Sequence in context: A197033 A245720 A229495 * A370198 A131921 A129105

Adjacent sequences: A390456 A390457 A390458 * A390460 A390461 A390462

Keyword

nonn,cons,more

Author

Amiram Eldar, Nov 06 2025

Status

approved