n+prime(n)+prime(prime(n)) is a triangular number, where prime(n) is the n-th prime.

Terms

a(0) =1a(1) =2a(2) =4a(3) =210a(4) =381a(5) =573a(6) =1009a(7) =1094a(8) =1117a(9) =2139a(10) =3123a(11) =4471a(12) =6459a(13) =7197a(14) =12534a(15) =13177a(16) =13335a(17) =13603a(18) =14178a(19) =19479a(20) =21512a(21) =23427a(22) =31833a(23) =35965a(24) =37924a(25) =38446a(26) =39726a(27) =55375a(28) =58851a(29) =59232