a(n) = Sum_{k=1..n} k*floor(n/k); also Sum_{k=1..n} sigma(k) where sigma(n) = sum of divisors of n (A000203).

A024916

a(n) = Sum_{k=1..n} k*floor(n/k); also Sum_{k=1..n} sigma(k) where sigma(n) = sum of divisors of n (A000203).

Terms

    a(0) =1a(1) =4a(2) =8a(3) =15a(4) =21a(5) =33a(6) =41a(7) =56a(8) =69a(9) =87a(10) =99a(11) =127a(12) =141a(13) =165a(14) =189a(15) =220a(16) =238a(17) =277a(18) =297a(19) =339a(20) =371a(21) =407a(22) =431a(23) =491a(24) =522a(25) =564a(26) =604a(27) =660a(28) =690a(29) =762

External references