1690920

Appears in sequences

• Number of length-6 0..k arrays connected end-around, with no sequence of L<n elements immediately followed by itself (periodic "squarefree").at n=10A215229
• G.f.: C(x,y)^2 - S(x,y)^2 = Sum_{n>=0} x^(2*n)*y/[Sum_{k=0..2*n+1} T(n,k)*y^k], where C(x,y) = Sum_{n>=0} x^(2*n) / Product_{k=1..2*n} (k + y) and S(x,y) = Sum_{n>=0} x^(2*n+1) / Product_{k=1..2*n+1} (k + y).at n=36A268647
• a(n) = [y^(n+1)] (n + y) * Product_{k=1..2*n} (k + y), for n >= 0.at n=5A322627