20138

Appears in sequences

• Numbers k such that 7*10^k + 3*R_k is prime, where R_k = 11...1 is the repunit (A002275) of length k.at n=19A056720
• Consider the graph with one central vertex connected to three outer vertices (a star graph). Then, a(n) is the minimum number of moves required to transfer a stack of n pegs from one outer vertex to another outer vertex, moving pegs to adjacent vertices, following the rules of the Towers of Hanoi.at n=40A291876
• Number of parts in all partitions of n with largest multiplicity four.at n=31A320374
• G.f. A(x) satisfies: [x^n] A(x)^(n+1) = [x^n] (1 + x*A(x)^(n+4))^(n+1) for n >= 0.at n=5A360236