21136

Appears in sequences

• Number of partitions of n with positive rank.at n=40A064173
• Number of permutations of 1..n with all differences of elements separated by distances 1 through 6 being respectively unique.at n=14A170812
• Sophie Germain 5-almost primes.at n=43A211162
• Triangle read by rows: number of permutations of [1..n] with k progressions of rise 2, distance 1 and length 3 (n >= 0, k >= 0).at n=44A216716
• Number of partitions of n having population standard deviation > 1.at n=36A238619
• Number of partitions of n having population standard deviation >= 1.at n=36A238620
• a(n) is the number of regular hexagons with all six vertices (x,y,z) in the set {1,2,...,n}^3.at n=13A338322
• Number of iterations before a repeated value, or -1 if this never occurs, when starting at k = 1 and repeating k = k*n if k does not contain any adjacent equal digits, else k = k with all adjacent equal digits replaced by a single copy of the same digit.at n=12A368940
• Expansion of g^2/(1 + x^4*g^4), where g = 1+x*g^3 is the g.f. of A001764.at n=7A391303