27281

Properties

Appears in sequences

• a(n) = ceiling(n*phi^15), where phi is the golden ratio, A001622.at n=20A004970
• Primes p such that x^48 = 2 has no solution mod p, but x^24 = 2 has a solution mod p.at n=34A059669
• Least k such that there are no middle divisors of k (A071090) through k+n.at n=17A071563
• Least k such that there are no middle divisors of k (A071090) through k+n.at n=18A071563
• Primes p such that p and p+2 are twin primes and also the strings 987654321p and 987654321p+2 are twin primes.at n=12A103818
• a(n) = numerator of sum of reciprocals of the terms of the continued fraction for H(n) = Sum_{k=1..n} 1/k.at n=26A112286
• Sophie Germain primes in A154939.at n=23A154941
• Number of n X 3 0..1 arrays with rows and columns unimodal and antidiagonals nondecreasing.at n=13A223772
• a(n) is a prime number that cannot be the center term of a length 3 arithmetic progression prime group with a common difference whose number of runs in binary expansion is 2.at n=29A231387
• Tenth prime p such that (p+n)^2+n is prime but (p+j)^2+j is not prime for all 0<j<n.at n=18A238682
• Numbers n such that the Crandall number C = A262961(n) has exactly one prime divisor p >= n/2.at n=16A265079
• Expansion of Product_{k>=1} 1 / (1 - x^k)^(5^(k-1)).at n=7A343350
• Primes p such that 2*p+1 and (2*p)^2+(2*p+1)^2 are also prime.at n=31A347110
• Primes p such that if q and r are the next two primes, 6*q-r, 6*q-p, 6*q+p and 6*q+r are all prime.at n=11A351636
• The reversing binary representation of the sum of the divisors of the n-th odd square: a(n) = A065621(A379223(n)).at n=40A379224
• Primes p such that p+1 is a triprime and 2*p+1 is prime.at n=42A386295
• Prime numbersat n=2987