a(n) = denominator( (1/(4*n + 2))*Sum_{i=0..2*n} (-1)^i/(2*i+1) ).
A392686
a(n) = denominator( (1/(4*n + 2))*Sum_{i=0..2*n} (-1)^i/(2*i+1) ).
Terms
- a(0) =2a(1) =90a(2) =3150a(3) =630630a(4) =13783770a(5) =320089770a(6) =43503109650
External references
- oeis: A392686