Euler's "numerus idoneus" (or "numeri idonei", or idoneal, or suitable, or convenient numbers).

Terms

a(0) =1a(1) =2a(2) =3a(3) =4a(4) =5a(5) =6a(6) =7a(7) =8a(8) =9a(9) =10a(10) =12a(11) =13a(12) =15a(13) =16a(14) =18a(15) =21a(16) =22a(17) =24a(18) =25a(19) =28a(20) =30a(21) =33a(22) =37a(23) =40a(24) =42a(25) =45a(26) =48a(27) =57a(28) =58a(29) =60