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 A359124 #12 Dec 20 2022 18:47:45
%S A359124 2,13,124,1235,12346,123457,1234568,12345679,123456790,12345678911,
%T A359124 1234567891012,123456789101113,12345678910111214,1234567891011121315,
%U A359124 123456789101112131416,12345678910111213141517,1234567891011121314151618,123456789101112131415161719,12345678910111213141516171820
%N A359124 Concatenate the decimal numbers 1,2,3,...,n, then add 1.
%C A359124 a(n) = A007908(n)+1.
%C A359124 Studied in A069048.
%t A359124 Table[FromDigits[Flatten[IntegerDigits/@Range[n]]]+1,{n,20}] (* _Harvey P. Dale_, Dec 20 2022 *)
%o A359124 (Python)
%o A359124 def a(n): return int("".join(map(str, range(1, n+1)))) + 1
%o A359124 print([a(n) for n in range(1, 20)]) # _Michael S. Branicky_, Dec 20 2022
%Y A359124 Cf. A007908, A069048, A359125.
%K A359124 nonn,base
%O A359124 1,1
%A A359124 _N. J. A. Sloane_, Dec 20 2022