18903

Appears in sequences

• Quadruples of different integers from [ 2,n ] with no common factors between triples.at n=30A015629
• Values of A038005 ending in 3.at n=25A038013
• Numbers k such that phi(k) is equal to A008473(k+1).at n=8A039781
• Numbers n such that (n+j) mod (2+j) = 1 for j from 0 to 5 and (n+6) mod 8 <> 1.at n=22A096024
• Number of lower triangles of an n X n integer array with each element differing from all of its diagonal, vertical, antidiagonal and horizontal neighbors by 4 or less and triangles differing by a constant counted only once.at n=2A195216
• T(n,k) is the number of lower triangles of an n X n integer array with each element differing from all of its diagonal, vertical, antidiagonal and horizontal neighbors by k or less and triangles differing by a constant counted only once.at n=17A195220
• Number of lower triangles of a 3 X 3 integer array with each element differing from all of its diagonal, vertical, antidiagonal and horizontal neighbors by n or less and triangles differing by a constant counted only once.at n=3A195221
• Triangle read by rows: T(n,k) is the number of secondary structures of size n having k stacks of even length (n>=0, k>=0).at n=31A202848
• Number of secondary structures of size n having no stacks of even length.at n=15A202849
• G.f.: Sum_{n>=0} x^n * (1+x)^A003188(n), where A003188(n) = n XOR [n/2] is the Gray code for n.at n=20A227526
• a(n) = Sum_{d|n} prime(n/d)^d.at n=13A309368