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 A038457 #10 Mar 22 2020 15:54:30 %S A038457 0,0,0,0,1,4,1,6,3,1,0,0,1,8,4,1,5,2,0,1,2,1,1,4,3,2,2,5,2,1,1,2,3,4, %T A038457 0,6,0,4,6,7,8,7,6,3,9,4,0,7,5,4,4,5,7,0,4,1,5,2,0,1,1,0,2,4,2,3,1,6, %U A038457 4,3,3,4,6,1,3,2,4,0,2,3,3,2,0,3,3,2,2,5,3,1,1,2,4,3,1,4,2,1,3,4,5 %N A038457 |First digit-last digit| for triangular numbers. %F A038457 a(n) = A040163(A000217(n)). - _Michel Marcus_, Sep 27 2013 %t A038457 Abs[IntegerDigits[#][[1]]-IntegerDigits[#][[-1]]]&/@Accumulate[ Range[ 0,120]] (* _Harvey P. Dale_, Mar 22 2020 *) %Y A038457 Cf. A000217. %K A038457 easy,nonn,base %O A038457 0,6 %A A038457 _Felice Russo_