137161

Appears in sequences

• Number of compositions of n avoiding the pattern 1111.at n=21A232464
• a(n) = Sum_{1 <= x_1, x_2, x_3 <= n} sigma( n/gcd(x_1, x_2, x_3, n) ).at n=18A373130
• a(n) = Sum_{1 <= x_1, x_2 <= n} sigma( ( n/gcd(x_1, x_2, n) )^2 ).at n=18A373132