34062336

Appears in sequences

• a(n) = phi(binomial(2n, n)).at n=14A066973
• a(n) = 16^n*[x^n]hypergeometric([3/2, -2*n], [3], -x).at n=5A254633
• a(n) is the determinant of the matrix with elements gcd(i,j) for 2 <= i,j <= n.at n=11A330967
• Smaller member of a noninfinitary amicable pair: numbers (k, m) such that nisigma(k) = m and nisigma(m) = k, where nisigma(k) is the sum of the noninfinitary divisors of k (A348271).at n=7A348343
• Expansion of e.g.f. arcsin(x)^2/(2*(1 - x)).at n=11A372324
• a(n) = Sum_{k=0..floor(n/3)} 2^k * 3^(n-3*k) * binomial(k,3*(n-3*k)).at n=38A392042