21240

Appears in sequences

• T(n,n-3), array T as in A054110.at n=37A054112
• a(n) = (2^(n-1)/(2n)!)*Product_{k=1..n} q(k) where q(n) is the denominator of B(2n), the 2n-th Bernoulli number.at n=28A069267
• First differences of A069475, successive differences of (n+1)^6-n^6.at n=27A069476
• Sum of aliquot divisors of Ramanujan's highly composite numbers.at n=19A072824
• Numbers that have exactly seven prime factors counted with multiplicity (A046308) whose digit reversal is different and also has 7 prime factors (with multiplicity).at n=1A109027
• Number of ways to build a contiguous building with n LEGO blocks of size 1 X 3 on top of a fixed block of the same size so that the building is flat, i.e., with all blocks in parallel position and symmetric after a rotation by 180 degrees.at n=12A123777
• a(0)=360, a(n)=a(n-1)+720 for n>=1.at n=29A140801
• 12 times hexagonal numbers: 12*n*(2*n-1).at n=30A143698
• Values of the difference d for 6 primes in arithmetic progression with the minimal start sequence {7 + j*d}, j = 0 to 5.at n=10A206040
• Values of the difference d for 7 primes in arithmetic progression with the minimal start sequence {7 + j*d}, j = 0 to 6.at n=6A206041
• Number of -3..3 arrays x(i) of n+1 elements i=1..n+1 with set{t,u,v in 0,1}((x[i+t]+x[j+u]+x[k+v])*(-1)^(t+u+v)) having four, six or eight distinct values for every i,j,k<=n.at n=5A211748
• Least m>0 for which m + n^2 is a square and m + triangular(n) is a triangular number (A000217).at n=31A267140
• Partial sums of the number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 595", based on the 5-celled von Neumann neighborhood.at n=27A273142
• Irregular table read by rows: The number of k-faced polyhedra, where k>=4, created when an n-prism, formed from two n-sided regular polygons joined by n adjacent rectangles, is internally cut by all the planes defined by any three of its vertices.at n=56A338801
• a(n) = Sum_{k=1..n} phi(n*k).at n=40A372608
• a(n) = (n!)^2 * [(x*y)^n] Product_{k>=1} (1 + (x^k + y^k)/k!).at n=8A382959