42839

Properties

Appears in sequences

• a(n) is smallest safe prime (A005385) such that a(n) + 12*n is the next safe prime, i.e., x = (a(n) - 1)/2 and x + 6*n are closest Sophie Germain primes.at n=31A059327
• Smaller of twin primes whose middle term is a multiple of A002110(4)=210.at n=34A060230
• Primes in which odd positioned digits are composite and even positioned digits are primes. The least significant digit is the taken to be the first digit.at n=27A083821
• Primes of the form k^3 - k - 1.at n=15A116581
• a(n) = n^3 - n - 1.at n=34A126420
• Primes which produce records in A157188, at index i=pi(a(n)) (pi=A000720).at n=7A157190
• Numbers m such that m mod k is k-1 for all k = 2..9.at n=16A166931
• a(n) = smallest prime of the form n*(n+1)*(n+2)...(n+k-1) - 1, or zero if no such a prime exists.at n=33A172125
• List of primes p1 such that (p1,p2) are twin primes where both 2*p1+p2 and p1+2*p2 are primes.at n=19A174920
• Primes of the form n^2 - 10.at n=16A201313
• The lesser of twin primes p1 such that 2*p1 + p2 is a prime number (A174913) and also the lesser of other twin primes in A174913.at n=5A242772
• Primes of the form (k - 1) * k * (k + 1) +- 1, k >= 1.at n=29A293861
• Primes p such that q=p^2+p+1 is prime and (q^2+q+1)/3 is prime.at n=46A322748
• Lesser of twin primes p >= 3 for which sigma(p+1)/sigma(p-1) reaches record value, where sigma(n) is the divisor sum function (A000203).at n=2A326391
• Lesser of twin primes p for which sigma(p+1)/sigma(p) reaches record value, where sigma(n) is the divisor sum function (A000203).at n=14A326392
• Lesser of twin primes p such that d(p+1) > d(q+1) for all lessers of twin primes q < p, where d(n) is the number of divisors of n (A000005).at n=18A328329
• The least prime p such that equation x = p*sopf(x) (where sopf(x) is the sum of distinct prime factors of x) has exactly n solutions in positive integers.at n=11A336296
• Primes p such that p^3 - 1 has 8 divisors.at n=37A341659
• The number of nonnegative integers that have a shortest divisor addition chain of length n.at n=20A352079
• a(n) is the least number that occurs exactly n times in A075255.at n=12A385964