a(n) = p(1)p(n) + p(2)p(n-1) + ... + p(k)p(n+1-k), where k = [ (n+1)/2 ], p = A000040 = the primes.

Terms

a(0) =4a(1) =6a(2) =19a(3) =29a(4) =68a(5) =94a(6) =177a(7) =231a(8) =400a(9) =484a(10) =753a(11) =903a(12) =1340a(13) =1552a(14) =2157a(15) =2489a(16) =3352a(17) =3784a(18) =5013a(19) =5515a(20) =7052a(21) =7758a(22) =9773a(23) =10575a(24) =13076a(25) =14076a(26) =17023a(27) =18339a(28) =21876a(29) =23414