a(n) = Sum_{k=1..n} sigma(k)*sigma(2*k), where sigma(n) = A000203(n) is the sum of the divisors of n.

A347108

a(n) = Sum_{k=1..n} sigma(k)*sigma(2*k), where sigma(n) = A000203(n) is the sum of the divisors of n.

Terms

    a(0) =3a(1) =24a(2) =72a(3) =177a(4) =285a(5) =621a(6) =813a(7) =1278a(8) =1785a(9) =2541a(10) =2973a(11) =4653a(12) =5241a(13) =6585a(14) =8313a(15) =10266a(16) =11238a(17) =14787a(18) =15987a(19) =19767a(20) =22839a(21) =25863a(22) =27591a(23) =35031a(24) =37914a(25) =42030a(26) =46830a(27) =53550a(28) =56250a(29) =68346

External references