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 A078568 #16 Aug 23 2022 18:34:32
%S A078568 11,1121,111321,11114321,1111154321,111111654321,11111117654321,
%T A078568 1111111187654321,111111111987654321,111111111110987654321,
%U A078568 111111111111110987654321,111111111111121110987654321
%N A078568 Repunits concatenated with A000422, where A000422 is the concatenation of numbers from n down to 1.
%C A078568 See A078569 for the primes arising in this sequence.
%H A078568 Harvey P. Dale, <a href="/A078568/b078568.txt">Table of n, a(n) for n = 1..277</a>
%t A078568 a[n_Integer] := Block[{repUn = Array[Array[1 &, #] &, {n}], nTo1 = Range[ Range@n, 1, -1]}, ToExpression/@ StringJoin/@ Map[ToString, Flatten/@ Thread@{repUn, nTo1}, {2}]]; a[100] (* or *)
%t A078568 a[n_Integer] := FromDigits /@ StringJoin /@ Table[ Join[ PadLeft[{}, i, "1"], ToString /@ Range[i, 1, -1]], {i, n}]; a[100] (* _Mikk Heidemaa_, May 03 2021 *)
%t A078568 Table[FromDigits[Join[PadRight[{},n,1],Flatten[IntegerDigits/@Range[n,1,-1]]]],{n,20}] (* _Harvey P. Dale_, Aug 23 2022 *)
%Y A078568 Cf. A002275, A000422, A078569.
%K A078568 base,nonn
%O A078568 1,1
%A A078568 _Jason Earls_, Nov 29 2002