18803

Properties

Appears in sequences

• G.f.: Product_{k>=1} (1 + x^(2*k - 1)) / (1 - x^(2*k)).at n=49A006950
• Reflectable emirps.at n=22A007628
• Primes setting records for earliest alphabetical position in American English.at n=14A050444
• Smallest prime p(k) such that the number of distinct prime divisors of all composite numbers between p(k) and p(k+1) is n.at n=47A075580
• Duplicate of A075580.at n=47A077132
• a(1) = 3; a(n) = smallest number such that the forward as well as the reverse n-th partial concatenation is a prime for n>1. (Reverse concatenation is taken term-wise and not digit-wise).at n=32A083993
• Least odd prime a(n) such that (a(n)*M(n))^2 + a(n)*M(n) - 1 is prime with M(n) = Mersenne-primes (A000043).at n=23A107709
• prime(k) for those k where floor((2*(prime(k+1)-prime(k))*PrimePi(k) mod (8*k))/k) = m with m = 10.at n=21A109564
• Number of ordered trees with n edges and no unary or binary nodes.at n=16A114997
• Prime sums of 6 positive 5th powers.at n=35A123035
• Primes p such that q-p = 36, where q is the next prime after p.at n=4A134117
• Primes congruent to 41 mod 53.at n=39A142571
• Primes congruent to 41 mod 59.at n=31A142768
• Primes congruent to 15 mod 61.at n=36A142813
• Primes of the form : 2*p+1=p1(prime), 2*p1+3=p2(prime), 2*p2+5=p3(prime).at n=36A143912
• Primes p such that continued fraction of (1 + sqrt(p))/2 has period 6: primes in A146331.at n=22A146351
• Primes p such that the multiplicative order of 2 modulo p is (p-1)/7.at n=20A152307
• Primes p such that p plus or minus the sum of the fourth powers of its digits is a prime in both cases.at n=25A179595
• Number of partitions of n containing a clique of size 2.at n=37A183559
• a(n)= least number k > a(n-1) such that k*(2^p-1)*(k*(2^p-1)+1)-1 is prime, where p = A000043(n) = Mersenne exponents.at n=23A200655