This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A034592 #5 Oct 06 2019 18:28:01 %S A034592 0,36,150,284,464,467,525,584,644,777,855,941,1058,1120,1179,1362, %T A034592 1788,1855,2368,2520,2547,2550,2576,2743,2988,3063,3273,3339,3410, %U A034592 3930,4054,4370,4739,4843,4910,5253,5445,5550,5671,5967,6512,6721,6987,7131,7216 %N A034592 Cycle of 2 steps possible for 'concatenate a(n) and nextprime(a(n)) is a prime'. %e A034592 a(n)=777 -> nextprime(a(n)) is 787 so '777787' is prime (=step 1); a(n2)=777787 -> nextprime(a(n2)) is 777817 so '777787777817' is prime (=step 2). %Y A034592 See also A034591-A034596, A030459. %K A034592 nonn,base %O A034592 0,2 %A A034592 _Patrick De Geest_, Oct 15 1998