a(0)=1; a(n) = sigma_1(n) + sigma_2(n) + sigma_3(n).

Terms

a(0) =1a(1) =3a(2) =17a(3) =42a(4) =101a(5) =158a(6) =314a(7) =402a(8) =685a(9) =861a(10) =1282a(11) =1466a(12) =2282a(13) =2382a(14) =3370a(15) =3812a(16) =5053a(17) =5222a(18) =7307a(19) =7242a(20) =9786a(21) =10164a(22) =12634a(23) =12722a(24) =17290a(25) =16433a(26) =20674a(27) =21300a(28) =26218a(29) =25262