A066968 Denominators of b(n) = (1/16)^n*(4/(8*n+1) - 2/(8*n+4) - 1/(8*n+5) - 1/(8*n+6)).

15, 6552, 5026560, 15590400, 4561108992, 244729774080, 15293220913152, 6027885936640, 2292288470384640, 143113842220597248, 2278611404728565760, 39351244081172840448, 3515953192213728460800, 2551413037895138672640

Offset: 0

Author

Benoit Cloitre, Aug 13 2002

Keywords

• easy
• frac
• nonn

Links

• G. C. Greubel, Table of n, a(n) for n = 0..815
• B. Gourevitch, L'univers de Pi

Crossrefs

Cf. A048581.

Programs

Mathematica

Denominator[Table[1/16^n (4/(8n+1)-2/(8n+4)-1/(8n+5)-1/(8n+6)),{n,0,20}]] (* Harvey P. Dale, Jul 16 2014 *)

PARI

a(n)=denominator(1/16^n*(4/(8*n+1)-2/(8*n+4)-1/(8*n+5)-1/(8*n+6)))

Formula

Sum_{k>=0} b(k) = Pi.