683067

Appears in sequences

• E.g.f. A(x,y) = cos((x - x*y)/2) / cos((x + x*y)/2) represented as a triangle, read by rows, where row n lists of coefficients T(n,k) of x^(2*n)*y^k/n! in A(x,y), for k=0..2*n.at n=42A272481
• a(n) equals the coefficient of x^(2*n)*y^n/(2*n)! in cos((x - x*y)/2) / cos((x + x*y)/2).at n=6A272482
• Expansion of g.f.: f'(t)/f(t), where f(t) = Sum_{p prime} t^p.at n=29A307977