27466

Appears in sequences

• Numbers k such that sopf(k) = 2*sopf(k+1), where sopf(k) = A008472.at n=27A064112
• Numbers k such that sigma(sigma(k) - k) = phi(sigma(k) + k).at n=20A074886
• Subdiagonal of array of n-gonal numbers A081422.at n=30A081423
• G.f.: A(x) = exp( 2*Sum_{n>=1} A006519(n)^2 * x^n/n ), where A006519(n) = highest power of 2 dividing n.at n=19A162581
• Total number of congruence subgroups of PSL(2,Z) of genus n.at n=11A258691