a(n) = Sum_{k=1..n} floor(n/k); also Sum_{k=1..n} d(k), where d = number of divisors (A000005); also number of solutions to x*y = z with 1 <= x,y,z <= n.
A006218
a(n) = Sum_{k=1..n} floor(n/k); also Sum_{k=1..n} d(k), where d = number of divisors (A000005); also number of solutions to x*y = z with 1 <= x,y,z <= n.
Terms
- a(0) =0a(1) =1a(2) =3a(3) =5a(4) =8a(5) =10a(6) =14a(7) =16a(8) =20a(9) =23a(10) =27a(11) =29a(12) =35a(13) =37a(14) =41a(15) =45a(16) =50a(17) =52a(18) =58a(19) =60a(20) =66a(21) =70a(22) =74a(23) =76a(24) =84a(25) =87a(26) =91a(27) =95a(28) =101a(29) =103
External references
- oeis: A006218