129889

Appears in sequences

• Strong pseudoprimes to base 21.at n=30A020247
• Brilliant Sarrus numbers.at n=13A086837
• Pseudotwinprimes p+2 for primes p such that p+2 divides p^(p+2)+2 and p+2 is composite.at n=31A100873
• Fermat pseudoprimes to base 2 with two prime factors.at n=36A214305
• Composite integers k such that 2^d == 2^(k/d) (mod k) for all d|k.at n=39A291601
• Numbers k such that 2^(k-1) == 1 (mod k) and lpf(k)-1 does not divide k-1.at n=8A316906
• Numbers k such that 2^(k-1) == 1 (mod k) and p-1 does not divide k-1 for every prime p dividing k.at n=6A316907
• 9-gonal numbers that are semiprimes.at n=17A356424
• a(n) is the smallest n-gonal number that is a Fermat pseudoprime to base 2 (A001567), or -1 if no such number exists.at n=6A371759