18600

Appears in sequences

• Harmonic or Ore numbers: numbers k such that the harmonic mean of the divisors of k is an integer.at n=12A001599
• Numbers whose divisors' harmonic and arithmetic means are both integers.at n=9A007340
• Numbers k such that the set of prime divisors of k is equal to the set of prime divisors of sigma(k).at n=12A027598
• Numbers whose base-4 representation contains exactly three 0's and four 2's.at n=28A045056
• Numbers k such that gcd(sigma(k),k) = k/5.at n=14A067237
• Coefficients in expansion of Eisenstein series -q*E'_2.at n=24A076835
• Sum of terms in n-th row of A077316.at n=23A077318
• a(n) = 18n^3 + 6n^2.at n=10A087887
• Duplicate of A007340.at n=9A090944
• Harmonic numbers (A001599) which are not perfect (A000396).at n=8A090945
• Expansion of g.f. (1 + x + 2*x^2)/((1 - x)^3*(1 - x^3)).at n=42A092498
• a(n) = (n+1)^2*(n+2)*(2*n+3)/6.at n=14A108678
• Number of base 20 n-digit numbers with adjacent digits differing by five or less.at n=4A126541
• Harmonic numbers that are not multiply-perfect.at n=6A140798
• a(n) = 1728*n - 408.at n=10A157266
• A partition product of Stirling_1 type [parameter k = -5] with biggest-part statistic (triangle read by rows).at n=17A157385
• Corresponding values of arithmetic means of divisors of numbers from A007340.at n=23A157848
• Regular coverings having dihedral voltage groups: see Kwak-Lee reference in A160870 for precise definition.at n=4A160875
• a(n) = ((2^b-1)/phi(n))*Sum_{d|n} Moebius(n/d)*d^(b-1) for b = 5.at n=5A160894
• Number of reduced words of length n in Coxeter group on 6 generators S_i with relations (S_i)^2 = (S_i S_j)^5 = I.at n=6A163317