28001

Properties

Appears in sequences

• Primes p such that x^48 = 2 has no solution mod p, but x^24 = 2 has a solution mod p.at n=35A059669
• a(1) = 1, a(n) = least prime divisor of b(n), where b(1) = 1, b(n) = n*b(n-1) + 1 = A002627(n).at n=17A096057
• Primes of the form 2^a * 5^b * 7^c + 1 for positive a, b, c.at n=11A114992
• Numbers k such that L(2*k + 1) is prime, where L(m) is a Lucas number.at n=37A117522
• Primes p1 such that p1^3+p2^2=pp are average of twin primes. p1 and p2 consecutive primes, p1 < p2.at n=20A138735
• Number of n X n binary arrays symmetric about both diagonal and antidiagonal with all ones connected only in a 0100-1110-0111-0010 pattern in any orientation.at n=15A146913
• Number of n X n binary arrays symmetric under 180 degree rotation with all ones connected only in a 1000-1001-1111 pattern in any orientation.at n=10A147138
• Lesser of two consecutive primes, p < q, such that both p*q+p-q and p*q-p+q are prime numbers.at n=34A154553
• Primes of the form 1000*k + 1.at n=9A156655
• a(n) = 70*n^2 + 1.at n=20A158734
• Primes of the form 250n + 1.at n=32A179231
• Primes which are the sum of three distinct positive cubes in two or more distinct ways.at n=25A180088
• A239461(n) / n^2.at n=27A239464
• Number of unlabeled rooted trees with n nodes where the outdegrees (branching factors) of at least one pair of adjacent nodes differ by at least two and the outdegrees of at least one pair of adjacent nodes are equal.at n=14A253244
• Primes of form n^2 + 2401.at n=19A256835
• Hyperartiads.at n=27A270798
• Artiads (A001583) congruent to 1 mod 50 and for which 5 is a quintic residue.at n=6A271210
• a(n) = a(n-1) + a(n-2) + a([n/2]) + a([n/3]) + ... + a([n/n]), where a(0) = 1, a(1) = 1, a(2) = 1.at n=19A298356
• G.f.: Sum_{n>=0} (n+1)*(n+2)/2 * (x + x^n)^n.at n=45A325998
• Numbers at the start of a run of exactly 2 consecutive primes that are Sophie Germain primes.at n=41A339475