A334746 Denominator of Sum_{k=1..n} 1/(prime(k) - 1)^2.

1, 4, 16, 144, 3600, 1800, 57600, 518400, 62726400, 3073593600, 614718720, 614718720, 3073593600, 3073593600, 1625931014400, 274782341433600, 231091949145657600, 231091949145657600, 231091949145657600, 231091949145657600, 77030649715219200

Offset: 1

Author

Petros Hadjicostas, May 11 2020

Keywords

• nonn
• frac

Comments

Lim_{n -> infinity} A119686(n)/a(n) = A086242.

Examples

			The first few fractions are 1, 5/4, 21/16, 193/144, 4861/3600, 2443/1800, 78401/57600, 707209/518400, ... = A119686/A334746.
		

Links

• Eric Weisstein's World of Mathematics, Prime Sums.

Crossrefs

Cf. A000040, A006093, A086242, A119686 (numerators).

Programs

Mathematica

Denominator @ Accumulate @ Table[1/(Prime[k] - 1)^2, {k, 1, 21}] (* Amiram Eldar, May 12 2020 *)

PARI

a(n) = denominator(sum(k=1, n, 1/(prime(k) - 1)^2)); \\ Michel Marcus, May 12 2020