18020

Appears in sequences

• a(n) = 1000*n + 20.at n=17A157510
• a(n) = n*(2*n^2 + 5*n + 1).at n=20A163832
• Number of connected regular graphs with n nodes and girth at least 4.at n=16A186724
• Number of (n+1) X 6 binary arrays with consecutive windows of two bits considered as a binary number nondecreasing in every row and column.at n=8A202332
• a(n)=f(a(n-1),a(n-2)+1,a(n-3)), where f(x,y,z)=yz+zx+xy and (a(1),a(2),a(3))=(0,0,1).at n=8A203762
• Number of (n+1) X (n+1) -6..6 symmetric matrices with every 2 X 2 subblock having sum zero and three distinct values.at n=9A211254
• Number of nX3 0..1 arrays with no element equal to more than two of its horizontal, diagonal or antidiagonal neighbors, with the exception of exactly two elements, and with new values introduced in order 0 sequentially upwards.at n=5A281558
• T(n,k)=Number of nXk 0..1 arrays with no element equal to more than two of its horizontal, diagonal or antidiagonal neighbors, with the exception of exactly two elements, and with new values introduced in order 0 sequentially upwards.at n=33A281563
• Number of 6Xn 0..1 arrays with no element equal to more than two of its horizontal, diagonal or antidiagonal neighbors, with the exception of exactly two elements, and with new values introduced in order 0 sequentially upwards.at n=2A281568
• The first Zagreb index of the Aztec diamond AZ(n) (see the Ramanes et al. reference, Theorem 2.1).at n=22A292344
• Practical numbers z such that z^2 = x^2 + y^2 for some practical numbers x and y with gcd(x,y,z) = 4.at n=29A294112
• a(n) = 4*(n - 1)*(16*n - 23) for n >= 1.at n=17A304378
• a(n) = Product_{d|n, d-1 is prime} (d-1)^(1+A286561(n,d-1)), where A286561(n,k) gives the k-valuation of n (for k > 1).at n=53A323155
• Numbers k such that (Sum of totatives of k) == 1 (mod Sum of primes dividing k with multiplicity).at n=39A340299
• a(n) = n^n - Sum_{k=1..n-2} f_k(n), with f_k(n)=( floor( (n^n - Sum_{t=1..k-1} f_t(n))^(1/(n-k)) ) )^(n-k).at n=46A349184
• Expansion of g.f. A(x) satisfying A(x) = 1 + x*(3*A(x)^2 - A(-x)^2)/2.at n=8A368634
• a(0) = 1; thereafter a(n) = 2*(6*n^2 - 3*n + 1).at n=39A386477