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 A113638 #26 Oct 14 2023 12:35:19
%S A113638 0,1,1,2,4,4,6,6,8,9,10,10,12,12,14,15,16,16,18,18,20,21,22,22,24,25,
%T A113638 26,27,28,28,30,30,32,33,34,35,36,36,38,39,40,40,42,42,44,45,46,46,48,
%U A113638 49,50,51,52,52,54,55,56,57,58,58,60,60,62,63,64,65,66,66,68,69,70,70,72
%N A113638 In the sequence of nonnegative integers subtract 1 from each prime number.
%F A113638 a(n) = A014684(n), n>0. - _R. J. Mathar_, Aug 13 2008
%t A113638 Table[If[PrimeQ[n],n-1,n],{n,0,80}] (* _Harvey P. Dale_, Sep 10 2017 *)
%o A113638 (Python)
%o A113638 from sympy import isprime
%o A113638 def A113638(n): return n-int(isprime(n)) # _Chai Wah Wu_, Oct 14 2023
%Y A113638 Cf. A014684.
%K A113638 easy,nonn
%O A113638 0,4
%A A113638 _Cino Hilliard_, Jan 15 2006
%E A113638 Name corrected by _Wolfdieter Lang_, Apr 22 2015