21857

Appears in sequences

• 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, 0), (-1, 0, 1), (0, 1, -1), (1, 0, -1), (1, 1, 1)}.at n=8A149689
• Number of partitions of n that include a pair of consecutive integers.at n=38A237666
• Lengths of complete iterations (direct and reverse branches) of the Kolakoski sequence A000002.at n=40A249508
• Define Z(1) = {1}, and Z(n+1) = Z(n) (+) { x+y, with x and y in Z(n) } for any n>0 (where (+) stands for the symmetric difference of two sets). Then a(n) gives the number of elements in Z(n).at n=15A263402
• Numerator of Sum_{k=1..n-1} 1/(k*(n-k))^2.at n=11A304581
• a(0) = 1; thereafter a(n) = 10*n^2 - 5*n + 2.at n=47A383466