a(n) = n*A340339(n)+b, where b = 1 if n is even or 2 if n is odd.

Terms

a(0) =5a(1) =11a(2) =23a(3) =53a(4) =97a(5) =139a(6) =331a(7) =569a(8) =659a(9) =971a(10) =1201a(11) =1669a(12) =2251a(13) =3347a(14) =3617a(15) =4337a(16) =4813a(17) =5527a(18) =6709a(19) =8861a(20) =9431a(21) =10979a(22) =12583a(23) =13513a(24) =14827a(25) =16823a(26) =18443a(27) =19853a(28) =21433a(29) =22291