171945

Appears in sequences

• a(n) = a(n-1) + Sum_{k=0..n-4} a(k)*a(n-4-k), a(0) = 1. Generalized Catalan Numbers.at n=23A023426
• Numbers k such that sigma(k) and sigma(k+1) are nontrivial powers (A065496).at n=28A065522