31853

Appears in sequences

• Numbers k such that the continued fraction for sqrt(k) has odd period and if the last term of the periodic part is deleted the two central terms are both 27.at n=5A031615
• Discriminants of real quadratic fields with class number 2 and related continued fraction period length of 13.at n=32A051978
• Triangle T(n,d) (listed row-wise: T(1,1)=1, T(2,1)=1, T(2,2)=1, T(3,1)=2, T(3,2)=2, T(3,3)=1, ...) giving the number of n-edge general plane trees with root degree d that are fixed by the six-fold application of Catalan Automorphisms A057511/A057512 (Deep rotation of general parenthesizations/plane trees).at n=68A079222
• a(0) = 2, a(1) = 3; for n>1, a(n) = a(n-2)^2 + a(n-1)^2.at n=4A113494
• Nodes of tree generated as follows: (1,2) is an edge, and if (x,y) is an edge, then (y, y^2 - x^2) and (y, y^2 + x^2) are edges.at n=22A228940
• G.f. A(x) satisfies: 1 = Sum_{n>=0} ( 1/(1-x)^n - A(x) )^n.at n=6A304639