51397

Appears in sequences

• Numbers n such that sigma (phi ( n ) ) = sigma (sigma (n ) ) where phi is Euler's totient and sigma is the multiplicative sum-of-divisors function.at n=25A065556
• Number of 2 X 2 nonsingular 0..n matrices with rows and columns in increasing order.at n=18A183762
• Triangle defined by g.f. A(x,y) = exp( Sum_{n>=1} x^n/n * Sum_{k=0..n} binomial(n*k, k^2) * y^k ), as read by rows.at n=31A228904