21187

Properties

Appears in sequences

• Primes that remain prime through 3 iterations of function f(x) = 5x + 8.at n=30A023286
• Discriminants of imaginary quadratic fields with class number 19 (negated).at n=36A046016
• a(n) = reverse(2^n) mod 2^n.at n=14A103166
• Primes congruent to 20 mod 61.at n=34A142818
• Primes obtained from other primes by pre-concatenating with 2.at n=41A165243
• G.f. satisfies: A(x) = 1/(1 - x*A(x)/(1 - x*A(x)^2/(1 - x*A(x)^4/(1 - x*A(x)^8/(1 - ...))))), a recursive continued fraction.at n=7A192739
• Records in A096335 (values).at n=37A221181
• Numbers k such that 9*10^k + 19 is prime.at n=27A272622
• Let F(g,p) be the frequency of g up to prime nextprime(p+1). Primes p such that F(2,p) = F(4,p) and g = 2 or 4.at n=36A274122
• Numbers n with the property that n^2 contains a sequence of four or more consecutive 8's.at n=10A301938
• Square array read by antidiagonals: T(n,k) is the number of simple labeled graphs G with vertex set V(G) = {v_1,...,v_n} along with a (coloring) function C:V(G) ->[k] such that v_i adjacent to v_j implies C(v_i) != C(v_j) and i<j implies C(v_i) <= C(v_j); n>=0, k>=0.at n=51A337161
• Numbers that are the sum of seven fourth powers in six or more ways.at n=25A345572
• Numbers that are the sum of seven fourth powers in exactly six ways.at n=20A345828
• Triangle T(n,k) read by rows, defined by the equation f(x, y) := Sum_{n, k} T(n, k) * y^k * x^n = 1/(1 - x*y - x^2*y*f(x, y+1)).at n=60A357438
• Primes p such that the concatenations of p and 123456789 in both orders are prime.at n=39A384174
• Prime numbersat n=2382