20407

Properties

Appears in sequences

• Expansion of 1/(1-x+2*x^2-x^3) in powers of x.at n=44A077954
• Expansion of 1/(1+x+2*x^2+x^3).at n=44A077979
• Least positive integer multiples of angle x such that their direction cosines form a unit vector: Sum_{k>0} cos(a(k)*x)^2 = 1, where a(1)=1 and x=2/3.at n=28A080140
• Primes in A051022.at n=33A092908
• Primes of the form 88x^2+32xy+127y^2.at n=32A140630
• a(n) = Sum_{k=0..n} (-1)^k * binomial(n, k) * A000931(n-k+4).at n=23A144413
• Primes p such that 8*p^2-2*p-1 divides Fibonacci(p).at n=18A159231
• Primes p such that p^2 - 8, p^2 - 6 and p^2 - 2 are prime.at n=10A176960
• Primes of the form 2n^2 + 5.at n=31A201474
• Primes of the form 7n^2 - 5.at n=12A201851
• a(n) = 2*a(n-1) - 3*a(n-2) + a(n-3), a(0) = 1, a(1) = 0, a(2) = -1.at n=31A233581
• Least prime p such that prime(p*n)-1 is a square, or 0 if no such p exists.at n=22A259764
• Primes p such that pi(p^2)*pi(q^2) is a square for some prime q < p, where pi(x) denotes the number of primes not exceeding x.at n=15A262700
• Numbers k such that (22*10^k + 71)/3 is prime.at n=21A286426
• Primes whose decimal expansion is of the form d_1+0+d_2+0+d_3+0+...+0+d_k where d_i are digits with 1 <= d_i <= 9, k > 1 and + stands for concatenation.at n=27A309488
• The prime numbers whose digit sum, adjacent digit sum concatenation, and adjacent digit difference concatenation are also primes.at n=48A330653
• Primes p = 8*r-1 such that all the prime factors of r are 7 mod 12.at n=40A339582
• Number of rooted bicolored trees on n unlabeled nodes such that black nodes are not adjacent to each other and every white node is adjacent to a black node.at n=10A339838
• Discriminants of imaginary quadratic fields with class number 41 (negated).at n=25A351679
• G.f. satisfies A(x) = 1 + x * A(x * (1 - x)).at n=13A360894