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 A077391 #10 May 05 2020 16:55:12 %S A077391 2,11,127,1021,10313,100237,1002931,10002331,100023331,1000023337, %T A077391 10000239937,100000233397,1000002339937,10000002339931, %U A077391 100000139991331,1000000023399331,10000000233993397,100000000293999997 %N A077391 Smallest n-digit prime which leaves a prime at every step if most significant digit and least significant digit are deleted until a one digit or two digit prime is obtained, or 0 if no such prime exists. %C A077391 Conjecture: No term is zero. %e A077391 a(6) = 100237: this is the smallest 6-digit number such that deleting MSD and LSD yields prime at every step, i.e. 100237, 0023, 02 all are primes. %Y A077391 Cf. A077390. %K A077391 base,nonn %O A077391 1,1 %A A077391 _Amarnath Murthy_, Nov 07 2002 %E A077391 More terms from _Daniel Starodubtsev_, May 05 2020