20670

Appears in sequences

• a(n) = n*(n+1)*(2*n+1)*(n^2+n+3)/30.at n=12A061927
• a(n) = ceiling(a(n-1)*4/3), with a(1) = 1.at n=32A087192
• 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=13A099008
• Numbers n such that n divides the denominator of 2n-th Bernoulli number.at n=36A106741
• Numbers k such that 6*prime(k) -+ {1,5} are all prime.at n=28A174393
• Number of labeled graphs on n nodes with degree set {2,4}.at n=7A228697
• Numbers divisible by prime(d) for each digit d in their base-9 representation, none of which may be zero.at n=49A256879
• Numbers m such that each of p=6*m+1, q=6*p+1, r=6*q+1 and s=6*r+1 is prime.at n=25A263311
• Number of length-4 0..n arrays with no repeated value greater than the previous repeated value.at n=10A269436
• Irregular triangle read by rows: T(n,k) is the number of k-regular graphs on n labeled nodes with loops allowed, n >= 1, 0 <= k <= n + 1.at n=37A333158
• The number of vertices on a concave circular triangle formed by the straight line segments mutually connecting all vertices and all points that divide the sides into n equal parts.at n=14A340686
• Number of odd Motzkin n-paths, i.e., Motzkin n-paths with an odd number of up steps.at n=13A343386
• Products of 5 distinct primes that are sandwiched between squarefree semiprime numbers.at n=16A376949