20908

Appears in sequences

• Numbers whose base-12 representation has exactly 5 runs.at n=14A043654
• Expansion of (1-x)^(-1)/(1-2*x-x^2-2*x^3).at n=10A077848
• G.f. A(x) satisfies A(x) = 1+x*A(x)+x^2*A(x)^2+2*x^3*A(x)^3.at n=10A186239
• Sequence a(n) = 3 + 5*A001519(n+1) appearing in a certain three circle touching problem, together with A246638.at n=9A246639
• Number of length 2+2 0..n arrays with the sum of second differences squared multiplied by some arrangement of +-1 equal to zero.at n=26A250321
• Number of active (ON, black) cells at stage 2^n-1 of the two-dimensional cellular automaton defined by "Rule 374", based on the 5-celled von Neumann neighborhood.at n=7A271458