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.
Select[DeleteDuplicates[Table[FromDigits[Flatten[IntegerDigits[Complement[Range[n], {2}]]]], {n, 50}]], PrimeQ[#] & ](* Robert Price, Nov 05 2018 *)
[Seqint(Reverse(&cat[Reverse(Intseq(k)): k in [2..n]])): n in [2..20]]; // Vincenzo Librandi, Oct 29 2018
Table[FromDigits[Flatten[IntegerDigits[Range[2, n]]]], {n, 2, 19}] (* Robert Price, Oct 28 2018 *)
def a(n): return int("".join(map(str, range(2, n+1))))
print([a(n) for n in range(2, 20)]) # Michael S. Branicky, Feb 23 2021
The first two terms correspond to the primes 13 and 134567891011121314151617181920212223242526272829303132333435363738394041 (see A262298). a(3) corresponds to a prime ending in 103, with 200 digits, a(4) to a probable prime ending in 1713, with 5744 digits, and a(5) to a probable prime ending in 2769, with 9968 digits. These three terms were found by _David Broadhurst_ on Oct 09 2015.
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