20333

Properties

Appears in sequences

• Numbers k such that the continued fraction for sqrt(k) has odd period and if the last term of the periodic part is deleted the two central terms are both 21.at n=8A031609
• Discriminants of real quadratic fields with class number 1 and related continued fraction period length of 21.at n=26A051962
• Denominators of convergents to Pi by Farey fractions.at n=47A063673
• Smallest prime obtained by appending 3's to k, where k runs through the numbers not divisible by 3, or -1 if no such prime exists.at n=13A112394
• Triangle read by rows in which row n gives list of prime factors of p^p + 1 where p = prime(n).at n=22A125136
• Primes congruent to 20 mod 61.at n=33A142818
• Primes containing the string 333.at n=11A166581
• Primes of the form 5*x^2 - 2*y^2, where x and y are successive natural numbers.at n=13A177077
• Primes with exactly three 3's.at n=23A178552
• G.f. satisfies: Sum_{n>=0} x^n*A_{n}(x) = x + x^2, where A_{n+1}(x) = A_{n}(A(x)) denotes iteration with A_0(x)=x.at n=14A180023
• Maximum values occurring in each row of A233270: a(n) = A233270(A233268(n) - A234020(n)).at n=18A234019
• Primes having only {0, 2, 3} as digits.at n=14A260125
• Primes of the form k*(k+2)/3 - 3, k>2.at n=28A262203
• Odd primes p with the property that gcd(ord_p q: prime q divides p-1) = 1.at n=18A295975
• Primes p such that, if q is the next prime, p^2 + q is a prime times a power of 10.at n=21A352852
• Number of crossings in a regular drawing of a complete bipartite graph where the vertex positions on each part equal the Farey series of order n.at n=6A359691
• Primes in A239237.at n=10A361252
• Smallest prime obtained by appending one or more 3's to n, or -1 if no such prime exists.at n=19A372056
• Primes having only {0, 2, 3, 4} as digits.at n=24A386041
• Primes having only {0, 2, 3, 5} as digits.at n=30A386042