OFFSET
0,1
COMMENTS
Machin's formula: Pi/4 = 4*arctan(1/5) - arctan(1/239).
Denominators are given in A096955.
REFERENCES
W. Walter, Analysis I (in German), Springer, 3. Auflage, 1992; p. 216.
LINKS
Wolfdieter Lang, More comments.
Eric Weisstein's World of Mathematics, Machin's Formula.
FORMULA
a(n)=numerator(M(n)), with M(n)=4*arctan(1/5, n) - arctan(1/239, n) with arctan(x, n):=sum((((-1)^k)*x^(2k+1))/(2*k+1), k=0..n).
EXAMPLE
a(2)/A096955(2) = 9569810428334921/12184551018734375 = .78540...
CROSSREFS
KEYWORD
nonn,frac,easy
AUTHOR
Wolfdieter Lang, Jul 23 2004
STATUS
approved