19279

Appears in sequences

• Number of Carmichael numbers (A002997) less than 10^n.at n=12A055553
• Hexagonal spiral sequence: sequence is written as a hexagonal spiral around a 'dummy' center, each entry is the sum of the row in the previous direction containing the previous entry.at n=23A063178
• Values of A063178 on folding point positions of the spiral.at n=12A063253
• Row sums of triangle A091499, in which A091499(n,k) equals the k-th term of the convolution of the two prior rows indexed by (n-k) and (k-1).at n=24A091501
• Number of ways to place zero or more nonadjacent 1,1 2,1 2,2 3,1 4,0 4,1 5,1 polyhexes in any orientation on a planar nXnXn triangular grid.at n=7A155319
• a(n) = n*(2*n^2 + 5*n + 1)/2.at n=25A162254
• Numbers n such that in Collatz (3x+1) trajectory of n, the number of terms < n equals number of terms > n.at n=41A217731
• Numbers n such that the decimal representation of the Elias delta code of n is a palindromic prime.at n=2A281496