18275

Appears in sequences

• Quadruples of different integers from [ 1,n ] with no common factors between pairs.at n=43A015623
• dot_product(n,n-1,...2,1)*(6,7,...,n,1,2,3,4,5).at n=37A026063
• Numbers n such that sum k/d(k) is an integer, where d(k) is the k-th divisor of n (the divisors of n are in increasing order).at n=8A073082
• a(n) = n*(n+7)*(n+8)/6.at n=43A111396
• G.f.: (1+x+x^2-sqrt(1+2x+3x^2-2x^3+x^4))/2.at n=22A129509
• Number of nX3 0..4 arrays with each element x equal to the number its horizontal and vertical neighbors equal to 0,3,1,1,1 for x=0,1,2,3,4.at n=10A197618
• Number of -2..2 arrays x(i) of n+1 elements i=1..n+1 with x(i)+x(j), x(i+1)+x(j+1), -(x(i)+x(j+1)), and -(x(i+1)+x(j)) having one or three distinct values for every i<=n and j<=n.at n=9A211460
• Irregular array read by rows. a(n) is the largest element in the primitive Collatz-like 3x-k cycle associated with A226623(n).at n=26A226624
• G.f. A(x) satisfies: A(x) = x + x^2 + x^3 + x^4 + x^5 * (1 + A(A(x))).at n=17A308032
• Numbers m such that m^2+1 is semiprime with (m-1)^2+1 and (m+1)^2+1 primes.at n=36A321985
• Expansion of Product_{k>=1} (Product_{j=1..k} 1/(1 - x^(k*j))^k).at n=16A327067
• a(1) = 27846; thereafter a(n+1) = a(n) # n, where # is an operation that cycles through division, addition, subtraction and multiplication.at n=15A327962
• Number of vertices in a regular drawing of the complete bipartite graph K_{n,n}.at n=19A331755
• Starts of runs of 3 consecutive integers whose exponent of least prime factor in their prime factorization is even.at n=32A365871
• Primitive terms of A389634.at n=36A389635