21216

Appears in sequences

• a(n) = floor(n*(n-1)*(n-2)*(n-3)/31).at n=30A011941
• Related to quartic factorial numbers A007696.at n=4A034255
• Multiplicity of highest weight (or singular) vectors associated with character chi_20 of Monster module.at n=41A034408
• Dirichlet convolution of sigma(n) with Bell numbers.at n=9A034765
• A convolution triangle of numbers obtained from A034255.at n=10A048882
• Number of polyhexes with n cells that tile the plane by 180-degree rotation (Conway criterion).at n=10A075211
• Sums of terms of groups in A075626.at n=33A075629
• Coefficients of power series that satisfies A(x)^4 - 16x*A(x)^5 = 1, A(0)=1.at n=4A078533
• Expansion of (1 - x + 2*x^2) / (1 - x^3 + x^4).at n=59A110062
• Site series for second perpendicular moment of Kagome lattice.at n=13A120552
• Rectangular array of coefficients in successive iterations of x*exp(x), as read by antidiagonals.at n=49A174480
• a(n) = coefficient of x^n/(n-1)! in the (n+1)-th iteration of x*exp(x) for n>=1.at n=4A174483
• a(n) = coefficient of x^n/(n-1)! in the 6-fold iteration of x*exp(x).at n=4A174496
• Numbers of the form p^5*q*r*s where p, q, r, and s are distinct primes.at n=25A179704
• Record (maximal) gaps between prime triples (p, p+2, p+6).at n=34A201598
• Sum_{0<j<k<=n} P(k)-P(j), where P(j)=A065091(j) is the j-th odd prime.at n=29A206803
• Nonnegative values x of solutions (x, y) to the Diophantine equation x^2 + (x+289)^2 = y^2.at n=13A207059
• a(n) = Pell(n)*A034896(n) for n >= 1, with a(0)=1, where A034896 lists the number of solutions to a^2 + b^2 + 3*c^2 + 3*d^2 = n.at n=8A209451
• Numbers n such that sigma(tau(phi(n))) = tau(phi(sigma(n))) = phi(sigma(tau(n))).at n=7A218006
• Triangle S(n,k) by rows: coefficients of 4^((n-1)/2)*(x^(1/4)*d/dx)^n when n is odd, and of 4^(n/2)*(x^(3/4)*d/dx)^n when n is even.at n=26A223170