Index in A375564 where n-th group of successive primes ends.

Terms

a(0) =3a(1) =9a(2) =21a(3) =45a(4) =92a(5) =177a(6) =351a(7) =702a(8) =1379a(9) =2724a(10) =5412a(11) =10787a(12) =21502a(13) =42958a(14) =85791a(15) =171441a(16) =342216a(17) =683462a(18) =1365580a(19) =2729447a(20) =5456194a(21) =10908253a(22) =21812343a(23) =43616683a(24) =87223016a(25) =174430392