20813

Appears in sequences

• Discriminants of real quadratic fields with class number 2 and related continued fraction period length of 19.at n=11A051984
• a(n+1) is the smallest number > a(n) such that the digits of a(n)^2 are all (with multiplicity) contained in the digits of a(n+1)^2, with a(0)=2.at n=14A067975
• Centered 22-gonal numbers.at n=43A069173
• Expansion of (1-x)/(1+x-x^2-2*x^3).at n=45A078041
• Binomial row sums of triangle A191490.at n=6A191493
• Self-inverse permutation of natural numbers: complementary pair ludic/nonludic numbers (A003309/A192607) entangled with the same pair in the opposite order, nonludic/ludic. See Formula.at n=63A235491
• Partial sums of the number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 659", based on the 5-celled von Neumann neighborhood.at n=24A273386
• G.f. A(x) satisfies: A(x) = 1/(1 + (-x)^a(0)/(1 + (-x)^a(1)/(1 + (-x)^a(2)/(1 + (-x)^a(3)/(1 + ...))))), a continued fraction.at n=18A307543
• Regular triangle read by rows where T(n, k) is the number of set partitions of {1, ..., n} with no block containing k cyclically successive vertices, n >= 1, 2 <= k <= n + 1.at n=39A323955