123998

Appears in sequences

• Number of modes of connections of 2n points.at n=9A006605
• a(1) = 2, a(n+1) = a(n)-th squarefree number > 1.at n=23A071255
• Double factorial primes; values k for which k!! + 1 is prime.at n=7A080778
• G.f. satisfies: A(x) = 1 + x*A(x)*A(-x) + x^2*A(x)^2*A(-x)^2.at n=19A143926
• Triangular array T(n,k) n,k>=0 is the number of k letter words formed using at most 1a,2b's,3c's,...,n#'s.at n=33A172528
• Square array T(n,k), n >= 0, k >= 0, read by antidiagonals downwards, where T(n,0) = 0^n and T(n,k) = k * Sum_{r=0..n} binomial(2*n+k,r) * binomial(r,n-r)/(2*n+k) for k > 0.at n=64A378292