1190400

Appears in sequences

• Numbers k such that phi(sigma(k)) = k.at n=12A001229
• Numbers k such that k = phi(sigma(phi(sigma(k)))).at n=26A067883
• Numbers k such that k = phi(sigma(phi(sigma(phi(sigma(k)))))).at n=27A067884
• a(n) = ((2^b-1)/phi(n))*Sum_{d|n} Moebius(n/d)*d^(b-1) for b = 5.at n=23A160894
• Number of (n+2) X 4 binary arrays avoiding patterns 001 and 101 in rows and columns.at n=27A202196
• Numbers which are the minimum of a cycle in the map x -> phi(sigma(x)).at n=29A376256