cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A371321 Decimal expansion of Sum_{k>=0} 1/A007018(k).

Original entry on oeis.org

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

Views

Author

Amiram Eldar, Mar 19 2024

Keywords

Comments

The corresponding alternating sum, Sum_{k>=0} (-1)^k/A007018(k), equals Cahen's constant (A118227).
Duverney et al. (2018) proved that this constant is transcendental.
Called the "Kellogg-Curtiss constant" by Sondow (2021), after the American mathematicians Oliver Dimon Kellogg (1878-1932) and David Raymond Curtiss (1878-1953).
The Engel expansion of this constant is 1 followed by the Sylvester sequence (A000058, see the Formula section).

Examples

			1.69103020675725397443566284314574179380857724257952...
		

References

  • Steven R. Finch, Mathematical Constants, Cambridge University Press, 2003, Section 6.7, p. 436.

Crossrefs

Programs

  • Mathematica
    s[0] = 2; s[n_] := s[n] = s[n - 1]^2 - s[n - 1] + 1; kmax = 1; FixedPoint[RealDigits[Sum[1/(s[k] - 1), {k, 0, kmax += 10}], 10, 120][[1]] &, kmax] (* after Jean-François Alcover at A118227 *)
  • PARI
    c = 1; 1 + suminf(k = 1, c += c^2; 1/c) \\ after Charles R Greathouse IV at A118227

Formula

Equals 1 + Sum_{k>=1} 1/(Product_{i=0..k-1} A000058(i)).