30240
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=15A001599
- a(n) = n!/5!.at n=5A001725
- Quadruple factorial numbers: a(n) = (2n)!/n!.at n=5A001813
- Denominators of coefficients for central differences M_{4}^(2*n).at n=3A002676
- Expansion of Eisenstein series E_4(q) (alternate convention E_2(q)); theta series of E_8 lattice.at n=5A004009
- Theta series of {E_6}* lattice.at n=41A005129
- a(n) = binomial(n,2)!/n!.at n=2A006473
- Numbers whose divisors' harmonic and arithmetic means are both integers.at n=12A007340
- a(n) = first n-fold perfect (or n-multiperfect) number.at n=3A007539
- Quadruple factorial numbers n!!!!: a(n) = n*a(n-4).at n=18A007662
- Multiply-perfect numbers: n divides sigma(n).at n=7A007691
- Theta series of direct sum of 3 copies of hexagonal lattice.at n=29A008654
- Theta series of direct sum of 3 copies of hexagonal lattice.at n=33A008654
- Area of more than one Pythagorean triangle.at n=23A009127
- a(n) is the concatenation of n and 8n.at n=29A009470
- The number of permutations of n cards in which 2 is the first card hit and 3 the next hit after 2.at n=7A018931
- Let sigma_m (n) be result of applying sum-of-divisors function m times to n; call n (m,k)-perfect if sigma_m (n) = k*n; sequence gives the (4,k)-perfect numbers.at n=51A019293
- Numerator of n*(n-2)*(2*n-1)/(2*(n-1)).at n=30A022997
- Numbers k such that sigma(k) >= 4*k.at n=1A023198
- Theta series of A*_8 lattice.at n=45A023920