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 A187871 #24 Nov 29 2021 01:39:37 %S A187871 1,12,123,1234,14325,143256,1234765,12347658,123476589,10123476589, %T A187871 1103211658947,101121123476589,11013432111276589,1011211231458941367, %U A187871 110134151432111276589,10112112151431613476589,1101316151417121123476589,101121118131615141723476589 %N A187871 a(1)=1; for n > 1, a(n) is the smallest number that is formed by arranging the decimal numbers "1", "2", ..., "n" in some order so that the sum of every pair of adjacent numbers "i" "j" is prime. %C A187871 A051237 and A187869 are the sequence that result if in addition we require that the number begins with "1" and ends with "n". %H A187871 Claudio Meller, <a href="http://www.misacertijos.com.ar/2011/03/lineas-con-numeros-de-1-n.html">Lineas con numeros de 1 a n</a>. %H A187871 Rémy Sigrist, <a href="/A187871/a187871.gp.txt">PARI program for A187871</a> %o A187871 (PARI) See Links section. %Y A187871 Cf. A051237, A187869. %K A187871 nonn,base %O A187871 1,2 %A A187871 _N. J. A. Sloane_, Mar 14 2011 %E A187871 a(6) to a(10) from _Claudio Meller_, Mar 14 2011 %E A187871 a(10) corrected by _Nathaniel Johnston_, Mar 15 2011 %E A187871 More terms from _Rémy Sigrist_, Nov 28 2021