1280664

Appears in sequences

• Prime power perfect numbers: If n = Product p_i^r_i let PPsigma(n) = Product {Sum p_i^s_i, 2<=s_i<=r_i, s_i is prime}; sequence gives numbers k such that PPsigma(k) = 2*k.at n=24A096290
• Triangle T(n,m)=m*n*binomial(m+n,m)^2/(2*(m+n)) read by rows.at n=20A131635
• Numbers k, excluding primes and squares of primes, such that gcd(k, numerator of H(k-1)) > 1, where the harmonic number H(j) = Sum_{i=1..j} 1/i.at n=14A228810