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 A134728 #8 Apr 04 2022 09:17:17
%S A134728 6,28496,8128335503368589869056,
%T A134728 13743869132823058430081399521282658455991569831744654692615953842176191561942608236107294793378084303638130997321548169216
%N A134728 Concatenation of next n perfect numbers.
%C A134728 The next term -- a(5) -- has 1592 digits. - _Harvey P. Dale_, Apr 04 2022
%H A134728 Omar E. Pol, <a href="http://www.polprimos.com">Determinacion geometrica de los numeros primos y perfectos</a>.
%t A134728 Module[{nn=5},FromDigits[Flatten[IntegerDigits/@#]]&/@TakeList[ PerfectNumber[ Range[ (nn(nn+1))/2]],Range[nn]]] (* _Harvey P. Dale_, Apr 04 2022 *)
%Y A134728 Cf. A053067, A132928, A133013. Perfect numbers: A000396.
%K A134728 base,easy,nonn
%O A134728 1,1
%A A134728 _Omar E. Pol_, Nov 12 2007