131337

Appears in sequences

• a(n) = Sum_{d|n} d * 4^(d-1).at n=7A359186
• Square array T(n,k), n>1 and k>1, read by antidiagonals in ascending order, giving the smallest n*k-digit number that, if arranged in an n X k matrix, forms a k-digit emirp (A006567) in each row and an n-digit emirp in each column, or -1 if no such number exists.at n=1A375234