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 A380785 #33 Mar 08 2025 17:31:23 %S A380785 181,13421,4831,25261,95651,43331,175141,1060781,404851,1648081, %T A380785 2597981,6085441,22151281,10270451,25180321,79817581,84549821, %U A380785 135045091,306099181,529811591,164710681,707429491,965524181,391995431,428045491,1516828721,4272226951,2337682591 %N A380785 Smallest of two consecutive primes p and q, both ending with 1, such that q - p = 10n, or -1 if no such primes exist. %e A380785 a(1) = 181, because 181 and 181 + 10 = 191 are two consecutive primes with the same last digit 1 and no smaller p has this property. %o A380785 (PARI) a(n) = my(p=11); while (!isprime(p) || ((nextprime(p+1)-p) != 10*n), p+=10); p; \\ _Michel Marcus_, Feb 20 2025 %Y A380785 Cf. A054681, A140791. %K A380785 nonn,base %O A380785 1,1 %A A380785 _Jean-Marc Rebert_, Feb 03 2025