2807136475

Appears in sequences

• Successive denominators of Wallis's approximation to Pi/2 (reduced).at n=18A001902
• Let W(n) = Product_{k=1..n} (1 - 1/(4*k^2)), the partial Wallis product (lim_{n->oo} W(n) = 2/Pi); then a(n) = numerator(W(n)).at n=9A069955
• Denominators of rationals related to John Wallis' product formula for Pi/2 (from his 'Arithmetica infinitorum' from 1659).at n=8A120995
• a(n) = denominator(r(n)) where r(n) = (n/2)*(Pi/2)^cos(Pi*(n-1))*((n/2-1/2)!/(n/2)!)^2.at n=19A380950