19729

Appears in sequences

• Pseudoprimes to base 17.at n=39A020145
• Strong pseudoprimes to base 17.at n=13A020243
• Strong pseudoprimes to base 19.at n=19A020245
• Strong pseudoprimes to base 32.at n=27A020258
• Strong pseudoprimes to base 92.at n=28A020318
• Numbers k such that the continued fraction for sqrt(k) has period 89.at n=20A020428
• Number of digits in n-th Fermat number (A000215).at n=16A057755
• Indices of primes in the sequence defined by A(0) = 29, A(n) = 10*A(n-1) - 21 for n > 0.at n=18A101965
• Zsigmondy numbers for a = 5, b = 3: Zs(n, 5, 3) is the greatest divisor of 5^n - 3^n (A005058) that is relatively prime to 5^m - 3^m for all positive integers m < n.at n=8A109347
• a(n) = (3*n+1)*(5*n+1).at n=36A144459
• Semiprimes which are the sum of three distinct positive cubes in two or more distinct ways.at n=28A180089
• a(n) = a(n-1) + a(a(n-1) mod n) + 1, a(0) = 1.at n=31A308576
• Number of digits of 2^^n.at n=6A319898