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 A259175 #20 Sep 08 2022 08:46:13
%S A259175 2,1,1,7,1,13,1,19,23,29,1,37,1,43,47,53,1,61,1,71,73,79,1,89,97,101,
%T A259175 103,107,1,113,1,131,137,139,149,151,1,163,167,173,1,181,1,193,197,
%U A259175 199,1,223,227,229,233,239,1,251,257,263,269,271,1,281,1,293,307,311
%N A259175 a(n) = 1 if n prime, otherwise prime(n).
%C A259175 The subsequence of prime terms is A007821. - _Michel Marcus_, Jun 20 2015
%e A259175 a(7) = 1 because 7 is prime.
%e A259175 a(8) = 19 because 8 is not prime and prime(8) = 19.
%t A259175 Table[If[PrimeQ[n], 1, Prime[n]], {n, 100}]
%o A259175 (Magma) [IsPrime(n) select 1 else NthPrime(n): n in [1..100]];
%Y A259175 Cf. A007821, A010051, A061397, A191558.
%K A259175 nonn,easy
%O A259175 1,1
%A A259175 _Vincenzo Librandi_, Jun 20 2015