51513

Appears in sequences

• Numbers k such that sigma(sigma(sigma(k))) == 6*sigma(k).at n=37A067065
• Take pairs (x,y) with Sum_{j = x..y} j = concatenation of x and y. Sort pairs on y then x. This sequence gives y of each pair.at n=23A070153
• The (1,6)-entry of the matrix M^n, where M is the 6 X 6 matrix {{1, 1, 1, 1, 1, 1},{1, 0, 0, 0, 1, 0},{1, 0, 0, 1, 0, 0},{1, 0, 1, 0, 0, 0},{1, 1, 0, 0, 0, 0}, {1, 0, 0, 0, 0, 0}}.at n=11A122365
• Expansion of Product_{k>=1} (1 + x^k)^ceiling(k/2).at n=30A319106
• Place n points in general position on each side of an equilateral triangle, and join every pair of the 3*n+3 boundary points by a chord; sequence gives number of edges in the resulting planar graph.at n=10A367119
• Expansion of g/(1 + x^2*g), where g = 1+x*g^4 is the g.f. of A002293.at n=7A387639