20988

Appears in sequences

• Number of n-node rooted unlabeled trees with exactly 3 edges at root and otherwise out-degree <= 2.at n=17A036658
• Number of 3 X 3 integer matrices with elements in the range [ -n,n ] which represent a six-fold rotation. Also the sequence for the corresponding six-fold rotoinversions.at n=3A053174
• Triangle T, read by rows, that satisfies: T(n,k) = [T^3](n-1,k) for n>k+1>=1, with T(n,n) = 1 and T(n+1,n) = n+1 for n>=0, where T^3 is the matrix cube of T.at n=29A109282
• Column 1 of triangle A109282.at n=6A109284
• Nearest integer to the space diagonal of the smallest (measured by the longest edge) primitive (gcd(a,b,c)=1) Euler bricks (a, b, c, sqrt(a^2 + b^2), sqrt(b^2 + c^2), sqrt(a^2 + c^2) are integers). If the space diagonal is an integer then the Euler brick is called a "perfect cuboid". There are no known perfect cuboids.at n=25A141029
• Number of strings of numbers x(i=1..7) in 0..n with sum i^3*x(i)^2 equal to 343*n^2.at n=21A184308
• Primitive integer length of the side of an origin-centered square that contains inside its boundary a point with integer coordinates that is an integer distance from three of the four corners.at n=15A215365
• Primitive values n such that the square with opposite corners (0,0) and (n,n) contains a point (x,y) with integer coordinates, with 0 < x,y < n, at an integer distance from three of the four corners.at n=29A260549
• Partial sums of the number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 249", based on the 5-celled von Neumann neighborhood.at n=29A271014
• G.f. satisfies: A(x - 3*A(x)^2) = x - 2*A(x)^2.at n=5A277307
• a(n) is the cardinality of S(n), the subset of partitions of n such that there are enough smaller parts to add together to be greater than a larger part.at n=36A338085
• Positive numbers whose square starts and ends with exactly 44, and no 444.at n=5A348831
• Draw a regular n-gon and the enclosing circle, then for each pair of vertices X, Y, draw a circle with diameter XY; the union of these figures is the graph H_n; sequence gives number of edges in H_n.at n=17A370979