640720

Appears in sequences

• Least integer m > 0 with pi(m*n) = sigma(m) + sigma(n), where pi(.) and sigma(.) are given by A000720 and A000203 respectively.at n=32A247673
• a(n) = Sum_{k=0..n} (n+1)*2^(n+k)*hypergeom([-n, k-n+1], [2], 1/2). Row sums of A337617.at n=7A337992