270269

Properties

Appears in sequences

• Primes formed by concatenating k with k-1.at n=32A052089
• Smaller of twin primes whose middle term is a multiple of A002110(5)=2310.at n=21A060231
• Smaller of twin primes whose mean (average) is a multiple of A002110(6)=30030.at n=1A060232
• Smaller of twin primes of the form P=j*P(i)#-1 and P=j*P(i)#+1 with 0 < j < P(i+1), where P(i) denotes i-th prime and P(i)# the i-th primorial number A002110(i).at n=15A087732
• Primes in A153257.at n=18A140719
• Primes that are the concatenation of k and k-1 for some k, where the concatenation of k-2 and k-3 is also prime.at n=5A156120
• Sophie Germain primes that are also highly cototient numbers.at n=25A209194
• Primes of the form 2*k!! - 1.at n=5A215780
• Primes p such that p^2 - p - 1, p^3 - p - 1 and p^4 - p - 1 are all prime.at n=17A236173
• Lesser of twin primes P(k) and P(k+1) such that Sd(P(k)) + Sd(P(k+1)) = Sd(k) + Sd(k+1), where Sd(x) is the sum of digits of x.at n=30A277111
• Numbers k such that phi(sigma(k))/k < phi(sigma(m))/m for all m < k, where sigma is the sum of divisors function (A000203) and phi is Euler's totient function (A000010).at n=33A293711
• Numbers k such that phi(psi(k))/k < phi(psi(m))/m for all m < k, where phi is Euler's totient function (A000010) and psi is the Dedekind psi function (A001615).at n=35A293713
• Numbers k where records occur for phi(k)/phi(k+1), where phi is the Euler totient function (A000010).at n=29A335070
• a(n) is the least number whose sum of digits in primorial base equals n.at n=43A343048
• Prime numbersat n=23665