1321920

Appears in sequences

• a(n) = n(n-1)(n-3)(n-6)...(n-t), where t is the largest triangular number less than n; number of factors in the product is ceiling((sqrt(1+8*n)-1)/2).at n=17A094261
• Triangle read by rows: numbers of isomers of unbranched a-4-catapolynonagons.at n=58A120650
• Unbranched a-4-catapolynonagons (see Brunvoll reference for precise definition).at n=7A121126
• Numbers m such that A049417(A049417(m)) = k*m for some k where A049417 is the infinitary sigma function.at n=31A318182
• a(n) is the least k such that A049417(A049417(k)) = n*k, where A049417 is the infinitary sigma function, or 0 if no such k exists.at n=6A318272