20604

Appears in sequences

• Numbers k such that k^2 + k + 4 is a palindrome.at n=11A027716
• Numbers k such that (k / sum of digits of k) and (k+1 / sum of digits of k+1) are both semiprime.at n=35A085774
• Records in A104883.at n=24A104884
• Partial sums of hexagonal numbers with prime indices.at n=14A117962
• a(n) = 2 + floor((1 + Sum_{j=1..n-1} a(j))/5).at n=51A120171
• 2n^4+6n^2+4 = 2(n^2+1)(n^2+2).at n=9A120571
• a(n) = prime(n)^2 - prime(n^2). Commutator of (primes, squares) at n.at n=42A123914
• Triangle read by rows: T(n,k) is the number of ordered trees with n edges having k odd-length branches starting at the root (0<=k<=n).at n=67A127538
• 12 times pentagonal numbers: a(n) = 6*n*(3*n-1).at n=34A153792
• Long leg B of primitive Pythagorean triangles such that perimeters are Averages of twin prime pairs, q=p+1, a=q^2-p^2, c=q^2+p^2, b=2*p*q, s=a+b+c, s-+1 are primes.at n=12A155174
• Row sums of triangle A182700.at n=17A182704
• Number of 5-step left-handed knight's tours (moves only out two, left one) on an n X n board summed over all starting positions.at n=18A187175
• G.f. satisfies: A(x) = (1 - 3*x*A(x))^2 * (4*A(x) - 3).at n=5A231616
• Number of ordered unlabeled rooted trees with n nodes such that the minimal outdegree of inner nodes equals 8.at n=26A244537
• Least common multiple of 7*n+1 and 7*n-1.at n=29A282286
• Expansion of ((eta(q)eta(q^3))/eta(q^2)^2)^2 in powers of q.at n=24A293389
• The number of regions inside a 2 by 1 ellipse formed by the straight line segments mutually connecting all points formed by dividing the ellipse into 2n equal angle sectors from its origin.at n=13A341688
• Triangle read by rows: T(n,k) is the number of embeddings on the sphere of 2-connected planar graphs with n nodes and k faces up to orientation preserving isomorphisms, n >= 3, k=2..2*n-4.at n=45A342059
• Denominator of the limiting density of residues attained by the Fibonacci sequence modulo powers of the n-th prime.at n=25A351000
• Irregular table read by rows: T(n,k) is the number of k-sided polygons formed, for k>=3, in a square when straight line segments connect the n+1 points along each edge that divide it into n equal parts to the n+1 points on the edge on the opposite side of the square.at n=47A355841