3720087

Appears in sequences

• a(n) = 7*3^n.at n=12A005032
• Triangle of coefficients in expansion of (1+9x)^n.at n=34A013616
• Numbers of form 7^i*9^j, with i, j >= 0.at n=34A025631
• Triangle whose (i,j)-th entry is binomial(i,j)*9^(i-j)*1^j.at n=29A038291
• a(n) = n*9^(n-1).at n=6A053540
• Let S(t) = 1 + s_1*t + s_2*t^2 + ... satisfy S' = -S/(2 + S); sequence gives denominators of s_n.at n=7A058956
• Smallest lucky number that is the product of n lucky numbers.at n=12A064703
• Treated as strings, the concatenation c of the prime factors of n, in increasing order, is an initial segment of n. Equivalently, n begins with c.at n=26A069154
• Triangular array T(n,k) read by rows, giving number of labeled free trees such that the root is smaller than all its children, with respect to the number n of vertices and to the label k of the root.at n=29A071211
• Number of spanning trees in K_{n}-e, the complete graph on n nodes minus an edge (n > 1).at n=7A071720
• Coefficient of the highest power of q in the expansion of nu(0)=1, nu(1)=b and for n >= 2, nu(n) = b*nu(n-1) + lambda*(n-1)_q*nu(n-2) with (b,lambda)=(2,3), where (n)_q = (1+q+...+q^(n-1)) and q is a root of unity.at n=26A072985
• Stirling2 triangle with scaled diagonals (powers of 9).at n=22A075504
• Second column of triangle A075504.at n=5A076008
• a(n) = (7*3^n - 4*0^n)/3.at n=13A082541
• a(n) = (8*9^n + (-9)^n)/9.at n=7A083226
• Duplicate of A082541.at n=13A083596
• Number of hex trees with n edges and having no nonroot nodes of outdegree 2.at n=13A126184
• a(n) = 3*a(n-1) for n>2; a(0)=1, a(1)=3, a(2)=7.at n=14A141495
• a(n) = 3*a(n-2) for n > 2; a(1) = 1; a(2) = 7.at n=25A166481
• a(n) = (n/4)*3^(n/2)*((1+sqrt(3))^2+(-1)^n*(1-sqrt(3))^2).at n=21A187273