218791

Appears in sequences

• Strong pseudoprimes to base 3.at n=31A020229
• Strong pseudoprimes to base 29.at n=35A020255
• Strong pseudoprimes to base 56.at n=31A020282
• Lexicographically earliest sequence of pairwise coprime triangular numbers.at n=29A034792
• Triangular numbers which are the product of two primes.at n=35A068443
• Pseudoprimes to bases 3 and 5.at n=22A083734
• Odd composites with increasing proportion of nontrivial non-witnesses of compositeness by the Miller-Rabin primality test.at n=10A090659
• Numbers k that divide Fibonacci(k-1) but do not divide Fibonacci(k) - 1.at n=21A094410
• Records in A111273.at n=19A113732
• Triangular numbers that are also brilliant (A078972).at n=28A113940
• Semiprimes in A006987(n), or semiprime binomial coefficients: C(n,k), 2 <= k <= n-2.at n=36A124000
• Numbers of the form p*q, p and q prime with q=2*p-1.at n=15A129521
• Odd numbers with increasing numbers of bases to which they are strong pseudoprimes.at n=22A141768
• Triangular numbers t such that all the digits needed to write the consecutive triangular numbers from 0 to t fill exactly an equilateral triangle (no holes, no overlaps).at n=32A158030
• Triangular numbers which are sums of three consecutive primes.at n=15A167788
• Triangular numbers which are sums of 5 consecutive primes.at n=14A173421
• Semiprimes k that divide Fibonacci(k-1).at n=25A177086
• G.f.: (t^5 + 2*t^4 + t^3 + 2*t^2 + t) / (t^6 + t^5 - 2*t^4 - 5*t^3 - 2*t^2 + t + 1).at n=22A180510
• Numbers m such that exactly half of the a such that 0<a<m and (a,m)=1 satisfy a^(m-1) == 1 (mod m).at n=31A191311
• Odd non-Carmichael numbers with increasing numbers of bases to which they are pseudoprimes.at n=31A194946