a(n) = least positive integer > a(n-1) and not a(j)*a(k) + a(k)*a(i) + a(i)*a(j) for 1<=i<=j<=k<=n.

Terms

a(0) =1a(1) =3a(2) =4a(3) =5a(4) =6a(5) =8a(6) =10a(7) =12a(8) =14a(9) =16a(10) =18a(11) =20a(12) =22a(13) =26a(14) =28a(15) =30a(16) =31a(17) =32a(18) =36a(19) =38a(20) =42a(21) =46a(22) =49a(23) =50a(24) =52a(25) =58a(26) =60a(27) =66a(28) =70a(29) =71