555731

Appears in sequences

• Expansion of (1+x)/cos(x).at n=11A009002
• Expansion of log(1 + tanh(x))/cos(x).at n=11A009391
• Expansion of e.g.f. x/cos(x) (odd powers only).at n=5A009843
• Expansion of e.g.f. x * (tan(x) + sec(x)).at n=10A065619
• a(n) = Sum_{k=0..n-1} 4^k*B(k)*C(n,k) where B(k) is the k-th Bernoulli number and C(n,k) = binomial(n,k).at n=11A083008
• Numerator of 2*n*A000111(n-1)/A000111(n): approximations of Pi, using Euler (up/down) numbers.at n=10A132049
• Numerator of Bernoulli(n, 1/4).at n=11A157817
• a(n) = Numerator((-1)^n*Euler(2*n)*(2*n+1)/(4^(2*n+1)-2^(2*n+1))), where Euler(n) = A122045(n).at n=5A160143
• Numerator of ez(n-1)*n!/(4^n-2^n) where ez(n) is the n-th coefficient of sec(t)+tan(t) for n>0, a(0) = 1.at n=11A193472
• a(n) = n*4^n*(-Z(1-n, 1/4)/2 + Z(1-n, 3/4)/2 - Z(1-n, 1)*(1 - 2^(-n))) for n > 0 and a(0) = 0, where Z(n, c) is the Hurwitz zeta function.at n=11A243963
• Triangle read by rows: T(n, k) = (-1)^(n-k) * (2*n + 1)! * [y^(2*k)] [x^(2*n+1)] arctan(sec(x*y)*tanh(x)).at n=20A371687
• Triangle read by rows: T(n, k) = (2*n + 1)! * [y^(2*k)] [x^(2*n+1)] arctan(sec(x*y)*sinh(x)).at n=20A371688