Concatenation of prime p and nextprime(p) is prime -> cycles of 2 steps possible.

Terms

a(0) =467a(1) =941a(2) =13681a(3) =14461a(4) =21787a(5) =22171a(6) =22369a(7) =24049a(8) =24151a(9) =25457a(10) =29333a(11) =37397a(12) =41221a(13) =42467a(14) =43481a(15) =46511a(16) =48023a(17) =54133a(18) =56681a(19) =68699a(20) =75883a(21) =85081a(22) =101341a(23) =103511a(24) =117443a(25) =120193a(26) =126199a(27) =137363a(28) =144323a(29) =145133