18388

Appears in sequences

• a(n) is the number of essentially different ways in which the integers 1,2,3,...,n can be arranged in a sequence such that all pairs of adjacent integers sum to a prime number. Rotations and reversals are counted only once.at n=13A073452
• Number of n-node labeled connected mating graphs, cf. A006024.at n=4A092430
• Number of partitions of n into parts with at most one part not greater than 2.at n=48A121659
• Numbers k such that k and k^2 use only the digits 1, 3, 4, 5 and 8.at n=4A137022
• Pascal-(1,8,1) array.at n=48A143683
• Pascal-(1,8,1) array.at n=51A143683
• A functionally symmetric Polynomial as a triangle of coefficients: p(x,n)=If[n == 0, 1, (x + 1)^n + 2^(n - 3)*Sum[(3^(m-1) + 2*m+(n-1) )*x^m*(1 + x^(n - 2*m)), {m, 1, n - 1}]].at n=48A146959
• A functionally symmetric Polynomial as a triangle of coefficients: p(x,n)=If[n == 0, 1, (x + 1)^n + 2^(n - 3)*Sum[(3^(m-1) + 2*m+(n-1) )*x^m*(1 + x^(n - 2*m)), {m, 1, n - 1}]].at n=51A146959
• Costas arrays such that the corresponding permutation is connected.at n=14A213339
• Number T(n,k) of set partitions of [n] with minimal block length multiplicity equal to k; triangle T(n,k), n>=0, 0<=k<=n, read by rows.at n=46A271424
• Number of set partitions of [n] with minimal block length multiplicity equal to one.at n=9A271426
• G.f. satisfies A(x) = 1 + x/(1 - x^3) * A(x/(1 - x^3)).at n=16A360890