42737

Properties

Appears in sequences

• Wagstaff numbers: numbers k such that (2^k + 1)/3 is prime.at n=29A000978
• Numbers k such that 2^k + 1 has just two distinct prime factors.at n=49A066263
• Numbers k such that 2^k + 1 is the product of two distinct primes.at n=47A073936
• Numbers k such that 2^k + 1 is a semiprime.at n=48A092559
• Indices of prime Jacobsthal numbers.at n=30A107036
• a(n) = 2n+1 if 2n+1 is prime else a(n) = least prime of the form (2n+1)(2n+3)...(2n+2k-1) + 2.at n=15A110337
• Number of 0..n arrays of length 3 with 0 never adjacent to n.at n=33A212836
• Numbers n such that (2^n+1)/3 is prime, but cannot be written in the form a^2 + 3*b^2.at n=14A216551
• Numbers k for which (2^k + 1)/F is prime where F is a Fermat number.at n=45A242076
• Primes p such that prime(p)^2 - 2 = prime(q) for some prime q.at n=40A261354
• Numbers k such that (2^k + 1)/(2 - (-1)^k) is a prime.at n=34A280083
• Primes equal to a centered heptagonal number plus 1.at n=18A285811
• Wagstaff numbers that are of the form 4*k + 1.at n=10A361563
• Prime numbersat n=4469