20556

Appears in sequences

• Theta series of direct sum of 6 copies of hexagonal lattice.at n=4A008657
• Numbers n such that 249*2^n-1 is prime.at n=18A050883
• Numbers k such that (k! + 3)/3 is prime.at n=20A089085
• a(1)=2, a(2)=2, a(n)=a(n-2)+floor(a(n-2)*a(n-1)/(a(n-2)+a(n-1))).at n=44A173091
• Number of line segments connecting exactly 7 points in an n X n grid of points.at n=38A177723
• Number of -2..2 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, five, six or eight distinct values for every i,j,k<=n.at n=8A211590
• Number of nondecreasing sequences of 6 1..n integers with no element dividing the sequence sum.at n=15A212873
• Irregular triangle read by rows: T(n,k) is the number of binary pattern classes in the (9,n)-rectangular grid with k '1's and (9n-k) '0's: two patterns are in same class if one of them can be obtained by a reflection or 180-degree rotation of the other.at n=35A228168
• Number of nX3 0..3 arrays x(i,j) with each element horizontally, vertically or antidiagonally next to at least one element with value (x(i,j)+1) mod 4 and at least one element with value (x(i,j)-1) mod 4, no adjacent elements equal, and upper left element zero.at n=9A230826
• Numbers k such that Bernoulli number B_{k} has denominator 1919190.at n=13A295595
• Consider binary words that begin with 1 such that the subword 00, whenever it appears, is followed by 111. Then a(n) counts such words at length n (including those where the string 111 is yet being completed - see Example).at n=18A340217
• Expansion of e.g.f. -log(1 - 3*x)/(3 * (1 + x)).at n=6A384202
• E.g.f. A(x) satisfies A(x) = exp( x * A(x*A(x)^3) ).at n=5A384740
• Square array A(n,k), n >= 0, k >= 0, read by antidiagonals downwards, where column k is the expansion of e.g.f. B(x)^k, where B(x) is the e.g.f. of A384740.at n=26A384742
• Consecutive states of the linear congruential pseudo-random number generator (625*s + 6571) mod 31104 when started at s=1.at n=17A385279