21615

Appears in sequences

• Numbers k such that the least term in the periodic part of the continued fraction for sqrt(k) is 49.at n=2A031727
• Odd numbers with exactly 4 distinct palindromic prime factors.at n=7A046406
• A class of Boolean functions of n variables and rank 3.at n=11A051361
• a(n) = n * (6*n^2 + 6*n + 1).at n=14A094421
• Number of walks within N^3 (the first octant of Z^3) starting at (0,0,0) and consisting of n steps taken from {(-1, -1, 1), (-1, 0, 1), (-1, 1, -1), (1, 0, 0), (1, 0, 1)}.at n=8A150310
• Number of (n+2) X (1+2) 0..1 arrays with each 3 X 3 subblock having clockwise perimeter pattern 00000001 00000011 or 00010001.at n=9A260537
• Number of permutations f of {1,...,prime(n)-1} with f(prime(n)-1) = prime(n)-1 and f(prime(n)-2) = prime(n)-2 such that 1/(f(1)*f(2)) + 1/(f(2)*f(3)) + ... + 1/(f(prime(n)-2)*f(prime(n)-1)) + 1/(f(prime(n)-1)*f(1)) == 0 (mod prime(n)^2).at n=4A346387
• Expansion of 1/((1-3*x) * (1-7*x))^(9/2).at n=3A387285