19679

Appears in sequences

• n^3*a(n) is the number of circles in complex projective plane tangent to three smooth curves of degree n in general position.at n=25A030653
• Numbers k such that 4*10^k - 9 is prime.at n=10A101396
• a(n) = (n+1)^((n+1)^n) - n^(n^(n-1)).at n=2A112406
• Semiprime nearest to 3^n. In case of a tie, choose the smaller.at n=9A117416
• a(0)=a(1)=1; for n>1, a(n) = 2*a(n-1) + 1 if a(n-1) and n are coprime, otherwise a(n) = a(n-1)/gcd(a(n-1),n).at n=31A133580
• a(n) = 3^n - 4.at n=9A168611
• Monotonic ordering of nonnegative differences 3^i-4^j, for 40>= i>=0, j>=0.at n=39A192147
• Value of concatenation of all suffixes of binary representation of n.at n=19A241426
• Absolute discriminants of complex quadratic fields with 3-class rank 2.at n=20A242862
• Numbers k such that sigma(k)! - 1 is prime, where sigma is A000203.at n=20A309548
• a(n) = numerator(Sum_{k=1..n} d(k+1)/d(k)), where d is the number of divisors function.at n=38A386925