Cubeful "year numbers" (such that phi(n) = 2 phi(sigma(n)): A137815).

Terms

a(0) =295569a(1) =295947a(2) =1586763a(3) =1811079a(4) =1964375a(5) =2069469a(6) =4473387a(7) =5854375a(8) =6820555a(9) =7285923a(10) =10936053a(11) =12233457a(12) =13260625a(13) =18029709a(14) =18052767a(15) =21153663a(16) =21576537a(17) =21604131a(18) =22182093a(19) =22877451a(20) =23744043a(21) =25536875a(22) =28340307a(23) =34102775