a(n) = sigma_2(n): sum of squares of divisors of n.

Terms

a(0) =1a(1) =5a(2) =10a(3) =21a(4) =26a(5) =50a(6) =50a(7) =85a(8) =91a(9) =130a(10) =122a(11) =210a(12) =170a(13) =250a(14) =260a(15) =341a(16) =290a(17) =455a(18) =362a(19) =546a(20) =500a(21) =610a(22) =530a(23) =850a(24) =651a(25) =850a(26) =820a(27) =1050a(28) =842a(29) =1300