695520
domain: N
Appears in sequences
- Harmonic or Ore numbers: numbers k such that the harmonic mean of the divisors of k is an integer.at n=27A001599
- Numbers whose divisors' harmonic and arithmetic means are both integers.at n=24A007340
- Fibonacci sequence beginning 0, 15.at n=24A022349
- Triangle T(n,k) read by rows: number of labeled trees with n nodes and k leaves, n >= 2, 2 <= k <= n.at n=41A055314
- Number of labeled trees with n nodes and 7 leaves.at n=2A055319
- Triangle T(n,k) of number of minimal 3-covers of a labeled n-set that cover k points of that set uniquely (k=3,..,n).at n=33A057964
- Harmonic numbers (A001599) which are not perfect (A000396).at n=23A090945
- Triangle read by rows: T(n,k) is the number of permutations p of [n] such that the length of the longest 2-stack sortable initial segment of p is equal to k.at n=49A094785
- Triangle read by rows: T(n,k) = the number of ascending runs of length k in the permutations of [n] for k <= n.at n=37A122843
- Harmonic numbers that are not multiply-perfect.at n=19A140798
- Number of runs or rising sequences of length 2 among all permutations of n.at n=7A141052
- Triangle T(n, k) = n!*StirlingS2(n, k)/binomial(n, k), read by rows.at n=39A156815
- Numbers m such that m = s|t = phi(s)*sigma(t) for some numbers s and t, where "|" denotes concatenation.at n=9A159000
- Row sums of triangle defined in A120852.at n=22A160963
- Numbers x such that there exist a pair y, n with x < y, x != n and y != n that makes {x,y,n,n} an amicable multiset.at n=0A273970
- Binomial coefficients binomial(n,k) = UV such that n>=2k and U > V, where gpf(U) <= k, gpf(V) > k (gpf(n)= is the greatest prime factor of n).at n=11A286981
- a(n) = (5*n + 5)*(5*n + 6)*(5*n + 7)/6.at n=31A300523
- Harmonic numbers m from A001599 such that m*(m-tau(m))/sigma(m) is an integer h, where k-tau(k) is the number of nondivisors of k (A049820), tau(k) is the number of divisors of k (A000005), and sigma(k) is the sum of the divisors of k (A000203).at n=9A325021
- Harmonic numbers (A001599) with a record harmonic mean of divisors.at n=14A335316
- Harmonic numbers k such that k*p is not a harmonic number for all the primes p that do not divide k.at n=11A335369