27647

Properties

Appears in sequences

• Class 1+ primes: primes of the form 2^i*3^j - 1 with i, j >= 0.at n=29A005105
• Primes that remain prime through 3 iterations of function f(x) = 5x + 4.at n=37A023284
• a(n) = s(1)t(n) + s(2)t(n-1) + ... + s(k)t(n+1-k), where k = [ (n+1)/2 ], s = (composite numbers), t = (primes).at n=34A024604
• a(n) is smallest prime such that a(n)+1 is a proper multiple of a(n-1)+1 [with a(1)=1].at n=9A058000
• T(3,n) with T(n,m) as in A063394.at n=9A063396
• a(n) = 48*n^2 - 1.at n=24A065532
• a(n) = A077700(n+1)/A077700(n).at n=18A077701
• a(1) = 1. For n>1, let x = a(n-1)+1; then a(n) is the first prime in the sequence 2*x-1, 2*x-3, 4*x-1, 4*x-3, 8*x-1, 8*x-3, ..., (2^k)*x-1, (2^k)*x-3, ...at n=9A083201
• Primes arising in A084402. a(n) = n-th partial product of A084402 - 1.at n=9A084403
• Primes of the form 3*m^2 - 1.at n=27A089682
• a(n) = a(n-1) + a(n-2) + a(n-1)*a(n-2) for n>=2; a(0)=2, a(1)=3.at n=5A100701
• Numerator of n-th term of the harmonic series after removal of all terms 1/m from Sum_{m=1..n} 1/m for which m contains a 9 in its decimal representation.at n=10A111935
• Least prime p such that sigma(x)=sigma(p) has exactly n solutions.at n=38A115374
• a(1)=2. For n >= 2, a(n) = a(n-1) + 1 + (the largest prime among the first n-1 terms of the sequence {a(k)}).at n=18A133489
• Primes of the form 12*n^2-1.at n=26A143830
• a(n) = 1024*n - 1.at n=26A158421
• Primes of the form 2^i*3^j - 1 with i + j = 13.at n=1A172315
• Primes of the form 13*n^2+3*n+1.at n=23A176783
• Primes of the form 2*k^3-1.at n=6A177105
• a(n) = 54n^3 - 1.at n=7A181968