81900

Appears in sequences

• Denominator in Feinler's formula for unsigned Bernoulli number |B_{2n}|.at n=12A002444
• Denominators of Cauchy numbers of second type (= Bernoulli numbers B_n^{(n)}).at n=24A002790
• Unitary harmonic numbers (those for which the unitary harmonic mean is an integer).at n=23A006086
• Denominators of Cauchy numbers of first type.at n=24A006233
• a(n) = n*(n+1)*(n+2)*(n+3)/6.at n=25A033488
• Least common multiple of all (k+1)'s, where the k's are the positive divisors of n.at n=23A057643
• Infinitary harmonic numbers: harmonic mean of infinitary divisors is an integer.at n=18A063947
• Bessel polynomial {y_n}'''(1).at n=5A065950
• Numbers k such that (1/k) * Sum_{d|k} d*sigma(d) is an integer.at n=20A069520
• Square array T(i,j) = Bernoulli(2i)*Bernoulli(2j) read by antidiagonals: denominators.at n=38A071021
• Square array T(i,j) = Bernoulli(2i)*Bernoulli(2j) read by antidiagonals: denominators.at n=42A071021
• One half of A075178.at n=24A075179
• Numbers k such that the total number of 1's in the binary expansion of all the divisors of k sets a new record.at n=40A093687
• Inverse of Riordan array (1/(1-x), x/(1-x)^4), A109960.at n=29A109962
• Triangle T(n, k) = (binomial(n,2))! / (k! * abs(k+1 - binomial(n,2))!), read by rows.at n=31A123146
• Smallest k such that the partial sums of the divisors of k (taken in increasing order) contain exactly n primes.at n=19A187822
• For k > a(n), the maximum number of steps that the Euclidean algorithm requires for computing (k,i), with i < k, is greater than n.at n=17A188224
• Numbers with prime factorization pqr^2s^2t^2.at n=1A190379
• a(n) is the smallest number k having n prime distinct divisors such that k is divisible by the square of the sum of its prime divisors.at n=2A190880
• a(n) = 5*binomial(4*n+5,n)/(4*n+5).at n=6A196678