19520

Appears in sequences

• Define the sequence S(a(0),a(1)) by a(n+2) is the least integer such that a(n+2)/a(n+1) > a(n+1)/a(n) for n >= 0. This is S(1,5).at n=6A018903
• First row of spectral array W(sqrt(5)-1).at n=11A022165
• Fibonacci sequence beginning 0, 32.at n=15A022366
• Numbers k such that the continued fraction for sqrt(k) has even period and if the last term of the periodic part is deleted the central term is 69.at n=39A031567
• Numbers whose base-3 representation contains exactly one 0 and no 1's.at n=32A044970
• Let (u1,u2) be successive untouchable numbers such that phi(u1) = phi(u2); sequence gives values of u2.at n=39A048190
• Consider all integer triples (i,j,k), j >= k > 0, with binomial(i+2,3) = j^3 + k^3, ordered by increasing i; sequence gives i values.at n=12A054205
• a(n) = Sum_{i=1..n, j=1..n, gcd(i,j)=1} (n+1-i)*(n+1-j).at n=17A115004
• Number of conjugated cycles composed of six carbons in (n,n)-nanotubes in terms of the number of naphthalene units.at n=7A121254
• Triangle read by rows: T(n,k) is the number of skew Dyck paths of semilength n and having k UDL's (n >= 0; 0 <= k <= floor((n+1)/2)).at n=22A128728
• Number of 3-step one space at a time bishop's tours on an n X n board summed over all starting positions.at n=41A187156
• Triangular array: the fission of ((x+2)^n) by (q(n,x)) given by q(n,x)=x^n+x^(n-1)+...+x+1.at n=42A193850
• Mirror of the triangle A193850.at n=38A193851
• Triangle read by rows, giving antidiagonals of an array of sequences representing the number of compositions of n when there are N types of ones (the sequences in the array begin (1, N, ...)).at n=61A228352
• Partial sums of A267326.at n=19A264390
• Partial sums of the number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 121", based on the 5-celled von Neumann neighborhood.at n=30A270208
• a(n) = phi(A291789(n)).at n=20A291805
• Number of partitions of n with eight kinds of 1.at n=9A320754
• Numbers whose product of prime indices is twice their sum of prime indices.at n=30A326151