Numbers n such that phi(n-1) + phi(n+1) = phi(2n).

Terms

a(0) =5a(1) =7a(2) =25a(3) =77a(4) =217a(5) =305a(6) =3665a(7) =4645a(8) =5065a(9) =8815a(10) =12205a(11) =12545a(12) =19877a(13) =20435a(14) =24235a(15) =29545a(16) =37735a(17) =47995a(18) =60115a(19) =72085a(20) =73025a(21) =77045a(22) =87475a(23) =121145a(24) =126055a(25) =129245a(26) =149755a(27) =190267a(28) =234635a(29) =247855