21132

Appears in sequences

• a(n) = Sum_{d | n} mu(n/d) * Bell(d-1).at n=9A034743
• Numbers n such that n*5^n - 1 is prime.at n=7A059676
• Expansion of 1/(1+6*x*c(x)), where c(x) = g.f. for Catalan numbers A000108.at n=6A127017
• Smallest numbers containing exactly n smaller numbers when written as English number names.at n=18A159453
• Riordan array (f(x), x*f(x)) where f(x) is the g.f. of A064613.at n=39A171568
• a(n) = 4*n^3 + 5*n^2 + 2*n + 1.at n=17A204674
• Number of 2 X 2 matrices having all terms in {-n,...,0,...,n} and determinant n.at n=32A211140
• Number of nX2 0..3 arrays with no element equal to the sum modulo 4 of elements to its left or elements above it.at n=5A238769
• Number of nX6 0..3 arrays with no element equal to the sum modulo 4 of elements to its left or elements above it.at n=1A238773
• T(n,k)=Number of nXk 0..3 arrays with no element equal to the sum modulo 4 of elements to its left or elements above it.at n=22A238775
• T(n,k)=Number of nXk 0..3 arrays with no element equal to the sum modulo 4 of elements to its left or elements above it.at n=26A238775
• Numbers k such that the product of their digits divides both k and R(k), where R(k) is the digits reverse of k.at n=32A277856
• Triangle read by rows: T(n,k) = number of chiral pairs of color patterns (set partitions) in a row of length n using exactly k colors (subsets).at n=49A320525
• Number of chiral pairs of color patterns (set partitions) in a row of length n using exactly 5 colors (subsets).at n=9A320528