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 A337613 #8 Sep 13 2020 16:42:36 %S A337613 1,3,7,9,71,11,13,17,19,73,79,711,31,37,97,111,113,117,119,713,131, %T A337613 137,171,173,179,717,197,311,313,719,731,317,319,737,371,373,797,379, %U A337613 7111,971,973,1111,979,7113,1113,1117,1119,7117,1131,1137,1171,1173,1179,7119,7131,1197,1311,1313,1317,1319,7137 %N A337613 Lexicographically earliest sequence of distinct positive integers such that the concatenation of any two successive digits forms a prime. %C A337613 Only the digits 1, 3, 7 and 9 are in the sequence as a term ending in 0, 2, 4, 5, 6 or 8 would not be prime. %e A337613 The first terms 1, 3, 7, 9, 71, 11, 13, 17,... form (when 2 successive digits are concatenated) the prime numbers 13, 37, 79, 97, 11, 11, 31, 17,... %Y A337613 Cf. A337614 (same idea, 3 successive digits). %K A337613 base,nonn %O A337613 1,2 %A A337613 _Eric Angelini_ and _Jean-Marc Falcoz_, Sep 05 2020