A331373 Decimal expansion of Sum_{k>=2} 1/(k! - 1).

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

Offset

1,2

Comments

Erdős was interested in the question whether this constant is irrational.

References

Paul Erdős, Some of my favourite unsolved problems, in A. Baker, B. Bollobás and A. Hajnal (eds.), A tribute to Paul Erdős, Cambridge University Press, 1990, p. 470.

Links

Table of n, a(n) for n=1..87.

Paul Erdős, On the irrationality of certain series: problems and results, in Alan Baker (ed.), New Advances in Transcendence Theory, Cambridge University Press, 1988, p. 102.

Paul Erdős and Ronald L. Graham, Old and new problems and results in combinatorial number theory, L'enseignement Mathématique, Université de Genève, 1980, p. 62.

Example

1.25349875569995347164336093790579894036923220833201...

Mathematica

RealDigits[Sum[1/(k! - 1), {k, 2, 300}], 10, 100][[1]]

Prog

(PARI) suminf(k=2, 1/(k!-1)) \\ Michel Marcus, May 03 2020

Crossrefs

Cf. A033312, A331372, A327826.

Sequence in context: A118460 A064788 A099521 * A120238 A245813 A146102

Adjacent sequences: A331370 A331371 A331372 * A331374 A331375 A331376

Keyword

nonn,cons

Author

Amiram Eldar, May 03 2020

Status

approved