a(1) = 2; a(n+1) = a(n) + p, where p is the largest prime <= a(n).

Terms

a(0) =2a(1) =4a(2) =7a(3) =14a(4) =27a(5) =50a(6) =97a(7) =194a(8) =387a(9) =770a(10) =1539a(11) =3070a(12) =6137a(13) =12270a(14) =24539a(15) =49072a(16) =98141a(17) =196270a(18) =392517a(19) =785020a(20) =1570037a(21) =3140044a(22) =6280085a(23) =12560152a(24) =25120299a(25) =50240588a(26) =100481175a(27) =200962342a(28) =401924669a(29) =803849308