From Goldbach conjecture: number of decompositions of 2n into an unordered sum of two odd primes.

Terms

a(0) =0a(1) =0a(2) =1a(3) =1a(4) =2a(5) =1a(6) =2a(7) =2a(8) =2a(9) =2a(10) =3a(11) =3a(12) =3a(13) =2a(14) =3a(15) =2a(16) =4a(17) =4a(18) =2a(19) =3a(20) =4a(21) =3a(22) =4a(23) =5a(24) =4a(25) =3a(26) =5a(27) =3a(28) =4a(29) =6