21576

Appears in sequences

• Number of connected functions on n labeled nodes.at n=5A001865
• Expansion of Product_{k>=1} (1-x^k)^32.at n=4A010837
• Positive numbers k such that k and 3*k are anagrams in base 8 (written in base 8).at n=12A023074
• Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 15 ones.at n=28A031783
• Triangle T(n,k) read by rows giving number of labeled mappings (or functional digraphs) from n points to themselves (endofunctions) with exactly k cycles, k=1..n.at n=15A060281
• Numbers that define integer Heronian triangles [a(n), prime(a(n)), A068968(n)] with area A068969(n).at n=35A068967
• Starting positions of strings of three 2's in the decimal expansion of Pi.at n=27A083606
• Numbers n not of the form i^2+(i+1)^2 such that there are integers a < b with a^2+(a+1)^2+...+(n-1)^2 = n^2+(n+1)^2+...+b^2.at n=20A094523
• E.g.f. : exp(6x)/(1-x).at n=5A108869
• Numbers that have exactly six prime factors counted with multiplicity (A046306) whose digit reversal is different and also has 6 prime factors (with multiplicity).at n=31A109026
• The number of 3D configurations of a labeled size 2*n "wurfel". A wurfel consists of a series of cubes held together on a looped string such that the string makes a right angle inside each cube. Ignoring the labels would make a wurfel a special kind of polycube in which the cubes can be cyclically ordered at consecutive right angles (equivalently, avoiding 3 consecutive collinear cubes).at n=7A117613
• Nonnegative values x of solutions (x, y) to the Diophantine equation x^2 + (x + 31)^2 = y^2.at n=12A118674
• Define an array by d(m, 0) = 1, d(m, 1) = m; d(m, k) = (m - k + 1) d(m+1, k-1) - (k-1) (m+1) d(m+2, k-2). Sequence gives d(n,3).at n=29A126935
• Number of walks within N^3 (the first octant of Z^3) starting at (0,0,0) and consisting of n steps taken from {(-1, 1, 1), (0, 1, 1), (1, -1, 1), (1, 1, -1), (1, 1, 1)}.at n=7A151018
• Number of permutations of floor(i*4/3), i=0..n-1, with all sums of 3 adjacent terms unique.at n=7A152316
• The number of parents of successive approximations used in a greedy approach to creating a Garden of Eden in Conway's Game of Life.at n=10A196447
• Triangular array read by rows: T(n,k) is the number of endofunctions f:{1,2,...,n}-> {1,2,...,n} whose largest component has exactly k nodes; n>=1, 1<=k<=n.at n=20A209324
• G.f. satisfies: A(x) = (1 + x*A(x)^2)^3.at n=5A212072
• Records in A224796.at n=35A224719
• Triangular array read by rows: T(n,k) is the number of size k components in the digraph representation of all functions f:{1,2,...,n}->{1,2,...,n}; n>=1, 1<=k<=n.at n=20A225723