56730

Appears in sequences

• a(n) = n*(n+1)*(2*n+1).at n=30A055112
• Numbers n such that the denominator of the 2n-th Bernoulli number is divisible by n but sum_{d|n} sigma(d)/phi(d) is not an integer.at n=22A099008
• Squarefree positive integers of the form u*v*(u^2-v^2) for some integer u,v.at n=29A147779
• a(n) = Sum_{0 < x,y,z <= n and gcd(x^2 + y^2 + z^2, n)=1} gcd(x^2 + y^2 + z^2 - 1, n).at n=30A239612
• Integer areas of integer-sided triangles where at least one of the three altitudes is of prime length.at n=30A256579
• Numbers that are product of a hexagonal number (A000384) and a square pyramidal numbers (A000330) in at least two ways.at n=19A306121
• a(1) = 24603, a(n) = n*a(n-1) but products that are not in A010784 are first reduced as in A320486 (see comments); continue until zero is reached.at n=61A321148
• Numbers k such that 423*2^k+1 is prime.at n=35A323112
• Number of minimum total dominating sets in the n-Goldberg graph.at n=28A382657
• Area of the unique primitive Pythagorean triple whose inradius is A002378(n) and such that its long leg and its hypotenuse are consecutive natural numbers.at n=5A384566
• a(n) = n*(n + 1)*(n^2 + 17*n + 54)/24.at n=30A387204
• a(n) = Sum_{k=0..n} (-1)^k * binomial(n+k+3,n-k) * Fibonacci(k+1).at n=14A390859