71613

Appears in sequences

• a(n)=2*(4^n-1)/denominator(B(2n)) where B(k) denotes the k-th Bernoulli number.at n=18A090648
• a(n) = a(n-1) + 2^n * a(n-2) with a(0) = 1 and a(1) = 1.at n=7A280294