680680

Appears in sequences

• a(n) = LCM(1,2,...,n) / n.at n=17A002944
• Denominator of n * n-th harmonic number.at n=17A027611
• a(n) = (2*n-1)*(3*n-1)*(4*n-1)*(5*n-1).at n=9A033590
• One eighth of 9-factorial numbers.at n=4A035022
• Number of ways to place two nonattacking queens on an n X n board.at n=34A036464
• a(n) = lcm(1..n) / ((n+1)(n+2)...(n+k)) where k is the largest number which gives an integral value.at n=16A069491
• Duplicate of A002944.at n=17A081529
• Given (1) f(h,j,a) = ( [ ((a/gcd(a,h)) / gcd(j+1,(a/gcd(a,h)))) * (h(j+1)) ] - [ ((a/gcd(a,h)) / gcd(j+1,(a/gcd(a,h)))) * (ja) ] ) / a then let (2) a(h) = d(h,j) = lcm( f(h,j,1) ... f(h,j,h) ).at n=8A091342
• a(n) = lcm_{k=1..n} (lcm(n,n-1,...,n-k+2,n-k+1)/lcm(1,2,...,k)).at n=16A093432
• a(n) = lcm{1, 2, ..., n}/(n*(n-1)), n >= 2.at n=17A099946
• Denominators of partial sums for a series for 2*Pi*sqrt(3)/9.at n=8A130554
• Let v = list of denominators of Farey series of order n (see A006843); let b(n) = Sum 1/(k+k'), where (k,k') are pairs of successive terms of v; a(n) = denominator of b(n).at n=8A278051
• Let v = list of denominators of Farey series of order n (see A006843); let b(n) = Sum k*k'/(k+k'), where (k,k') are pairs of successive terms of v; a(n) = denominator of b(n).at n=8A278561
• Number of nX4 0..1 arrays with each 1 adjacent to 3, 4 or 6 king-move neighboring 1s.at n=10A297016
• Irregular triangle T giving the coefficients of x^n = x^{2*e2 + 3*e3} of (1 + x^2 + x^3)^n, with the pair of nonnegative numbers [e2, e3] listed in row n of A321201, for n >= 2.at n=30A321203
• Numbers having at least three representations as multinomial coefficients M(n;lambda), where lambda is a partition of n into distinct parts.at n=36A325903
• Triangle read by rows T(n, k) = binomial(2*n, k) * binomial(3*n - k, 2*n).at n=32A357613
• a(n) is the smallest number with exactly n divisors that are centered n-gonal numbers.at n=6A358541
• Triangle T(n, m) = (n - m + 1)*C(2*n + 1, m)*C(2*n - m + 2, n - m + 1)/(2*n - m + 2).at n=38A360651
• Triangle T(n, m) = (n - m + 1)*C(2*n + 1, m)*C(2*n - m + 2, n - m + 1)/(2*n - m + 2).at n=42A360651