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 A331373 Decimal expansion of Sum_{k>=2} 1/(k! - 1). 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 (list; constant; graph; refs; listen; history; text; internal format)
 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 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. 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

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Last modified April 13 21:06 EDT 2021. Contains 342941 sequences. (Running on oeis4.)