20109

Appears in sequences

• Write log(2) as a binary fraction; read this from left to right and whenever a 1 appears, note the integer formed by reading leftwards from that 1.at n=7A099974
• A transform of the Catalan numbers with a simple Hankel transform.at n=31A157127
• Odd numbers k such that phi(k) and cototient(k) have the same prime signature.at n=24A280927
• a(0) = 1; a(n) = Sum_{k=0..floor((n-1)/4)} binomial(n-3*k-1,k) * a(k).at n=32A352043
• a(n) is the number of solid (3D) partitions of n with 2 layers and second layer a plane partition of 2.at n=13A378854