1474560

Appears in sequences

• Successive numerators of Wallis's approximation to Pi/2 (unreduced).at n=9A001900
• Denominators of coefficients of odd powers of x of the expansion of Bessel function J_1(x).at n=4A002474
• Denominators of an asymptotic expansion for the number of forests on n nodes (A001858).at n=10A006573
• Denominators in the Taylor expansion exp(cosec(x)-cot(x))=1 + x/2 + x^2/8 + x^3/16 + 3*x^4/128 + 37*x^5/3840 + 59*x^6/15360 + ...at n=8A013516
• a(0) = 1; for n > 0, a(n) = n!*4^n/2.at n=6A051711
• Numbers k such that, in the prime factorization of k, the product of exponents equals the product of prime factors.at n=35A054412
• a(n) = Product_{i=2..n} phi(i)/bigomega(i).at n=14A066988
• Products of exactly 18 primes (generalization of semiprimes).at n=10A069279
• Number of subsets of {1,.., n} containing no twin prime pairs.at n=21A089827
• Row sums of triangle A094280.at n=18A094283
• a(1) = 1, a(2) = (2*1)/1 = 2. a(n+1) = (n+1)*a(n) divided by the largest prime divisor of a(n).at n=19A100773
• Phi(binomial(2*n,n)*n^3).at n=8A131705
• Records in (A063375: Number of divisors of Fibonacci(n)).at n=18A154906
• Numerators of fractions in the approximation of the square root of 5 satisfying: a(n)= (a(n-1)+ c)/(a(n-1)+1); with c=5 and a(1)=0. Also product of the powers of two and five times the Fibonacci numbers.at n=12A163305
• The lower left triangle of the ED2 array A167560.at n=26A167569
• a(n) = n*(n-3)*2^(n-2).at n=15A178987
• a(n) = (n/4)*2^(n/2)*((1+sqrt(2))^2 + (-1)^n*(1-sqrt(2))^2).at n=30A187272
• a(n) = Sum_{0 < x,y,z,t <= n and gcd(x^2 + y^2 + z^2 + t^2, n)=1} gcd(x^2 + y^2 + z^2 + t^2 - 1, n).at n=29A239613
• Number of (n+2) X (n+2) 0..1 arrays with no 3 X 3 subblock diagonal sum 0 and no antidiagonal sum 3 and no row sum 0 or 3 and no column sum 0 or 3.at n=28A258958
• Number of orthogonal 3 X 3 matrices over the ring Z/nZ.at n=39A264083