20513

Appears in sequences

• Coordination sequence for MgNi2, Position Mg1.at n=35A009936
• Discriminants of real quadratic fields with class number 2 and related continued fraction period length of 19.at n=10A051984
• a(1) = 1; set of digits of a(n)^2 is a subset of the set of digits of a(n+1)^2.at n=26A066825
• Numbers k such that the largest prime factor of k is equal to the sum of primes dividing k+1 (with repetition).at n=22A071861
• Number of 8-almost primes 8ap such that 2^n < 8ap <= 2^(n+1).at n=20A120039
• Expansion of x/((1-x-x^3)*(1-x)^5).at n=14A144899
• Expansion of Product_{k > 0} (1 + f(k)*x^k), where f(1) = 1 and f(m) = prime(m-1) for m >= 2.at n=18A152006
• Number of nondecreasing arrangements of 7 numbers x(i) in -(n+5)..(n+5) with the sum of sign(x(i))*2^|x(i)| zero.at n=19A187991
• Numbers n such that n contains exactly 5 digits, all distinct, and n^2 contains exactly 9 distinct digits.at n=14A204691
• Number of length n+6 0..2 arrays with every seven consecutive terms having the maximum of some two terms equal to the minimum of the remaining five terms.at n=3A250148
• T(n,k)=Number of length n+6 0..k arrays with every seven consecutive terms having the maximum of some two terms equal to the minimum of the remaining five terms.at n=13A250154
• Number of length 4+6 0..n arrays with every seven consecutive terms having the maximum of some two terms equal to the minimum of the remaining five terms.at n=1A250158
• Numbers n for which the numbers 6n+1, 3n+2, 6n+7 are all odd composite squarefree numbers, but none are semiprimes.at n=34A263510
• a(n) = Sum_{k=0..n} binomial(n+1,k+1)*A001003(k).at n=7A277395
• Composite hypotenuses of primitive Pythagorean triangles (A120961) that are not circumdiameters of non-Pythagorean primitive Heronian triangles (A285579).at n=24A329148