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 A074842 #16 Sep 08 2022 08:45:07
%S A074842 111,222,333,444,555,666,777,888,999,101010,111111,121212,131313,
%T A074842 141414,151515,161616,171717,181818,191919,202020,212121,222222,
%U A074842 232323,242424,252525,262626,272727,282828,292929,303030,313131,323232,333333
%N A074842 Triplets: base 10 representation is the juxtaposition of three identical strings.
%t A074842 Table[FromDigits[Flatten[IntegerDigits/@PadRight[{},3,n]]],{n,40}] (* _Harvey P. Dale_, Aug 10 2019 *)
%o A074842 (UBASIC)
%o A074842 10 cls
%o A074842 30 for I=1 to 100
%o A074842 40 A=str(I)
%o A074842 50 C=A+A+A
%o A074842 60 B=val(cutspc(C))
%o A074842 80 print B
%o A074842 90 next
%o A074842 100 end
%o A074842 (Magma) [Seqint(Intseq(n) cat Intseq(n) cat Intseq(n)): n in [1..46]]; // _Vincenzo Librandi_, Feb 21 2014
%Y A074842 Cf. A020338.
%K A074842 easy,nonn,base
%O A074842 1,1
%A A074842 _Felice Russo_, Sep 10 2002