20667

Appears in sequences

• Number of unrooted triangulations of a quadrilateral with n internal nodes.at n=7A005500
• Composite numbers whose prime factors contain no digits other than 3 and 8.at n=20A036317
• Base 9 digits are, in order, the first n terms of the periodic sequence with initial period 3,1.at n=4A037588
• Base-9 palindromes that start with 3.at n=32A043030
• Numbers that are the product of 3 prime factors whose concatenation is a palindrome.at n=38A046452
• 3p^2 where p runs through the primes.at n=22A079705
• Odd numbers k such that A166100((k-1)/2)/k is not an integer.at n=23A166102
• Array T(n,k) read by antidiagonals: T(n,k) is the number of [n,k]-triangulations in the plane, n >= 0, k >= 0.at n=43A169808
• Number of nontrivial solutions (x,y,z) for each prime number p of the Fermat equation x^p + y^p + z^p = 0 mod (n) where n is prime of the form n = 2p + 1, and x, y, z are integers such that x < = y.at n=9A172426
• Numbers of the form 20*k+7 which are three times a square.at n=16A192328
• 3*h^2, where h is an odd integer not divisible by 3.at n=27A229852
• Numbers p^2*q, p > q odd primes such that q divides p+1.at n=16A350245
• Triangle read by rows: T(n,k) is the number of n-node connected unsensed planar maps with an external face and k triangular internal faces, n >= 3, 1 <= k <= 2*n - 5.at n=79A378103
• G.f. A(x) satisfies A(x/A(x)) = sqrt( A(x)/(1-x) ).at n=6A383373