531438

Appears in sequences

• Number of primitive (aperiodic) palindromes using a maximum of three different symbols.at n=22A056459
• Number of primitive (period n) periodic palindromes using a maximum of three different symbols.at n=22A056494
• The sequence lambda(3,n), where lambda is defined in A055203. Number of ways of placing n identifiable positive intervals with a total of exactly three starting and/or finishing points.at n=12A058809
• a(n) = (3^n-1)*(n+1)/4.at n=10A261064
• G.f. A(x,y) satisfies: Sum_{n=-oo...+oo} (x^n + y)^n = exp( (1-y) * A(x,y) ) / (1-y), where A(x,y) = Sum_{n>=1} x^n/n * Sum{k=0..n-1} T(n,k)*y^k, written here as a flattened triangle of coefficients T(n,k) read by rows.at n=77A321600
• Main diagonal of triangle A321600; a(n) = A321600(n,n-1) for n >= 1.at n=11A322116
• Triangle read by rows: T(n,k) is the number of sets of noncrossing paths of size k whose nodes are a subset of n nodes arranged in a circle with one node paths disallowed, 0 <= k <= floor(n/2).at n=43A390896