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 A100318 #10 Sep 08 2022 08:45:15 %S A100318 3,5,7,8,9,10,11,13,14,15,16,17,19,20,21,22,23,24,25,26,27,28,29,31, %T A100318 32,33,34,35,36,37,38,39,40,41,43,44,45,46,47,48,49,50,51,52,53,54,55, %U A100318 56,57,58,59,61,62,63,64,65,66,67,68,69,70,71,73,74,75,76,77,78,79,80,81 %N A100318 Numbers n such that at least one of n-1 and n+1 is composite. %C A100318 All odd numbers > 1 occur in this sequence. For the subsequence of even terms, see A100319. %H A100318 G. C. Greubel, <a href="/A100318/b100318.txt">Table of n, a(n) for n = 1..10000</a> %t A100318 Select[Range[3, 100], CompositeQ[#-1] || CompositeQ[#+1] &] (* _G. C. Greubel_, Apr 25 2019 *) %o A100318 (PARI) for(n=3,100,if(isprime(n-1)+isprime(n+1)<=1,print1(n,","))) %o A100318 (Magma) [n: n in [3..100] | not IsPrime(n-1) or not IsPrime(n+1) ]; // _G. C. Greubel_, Apr 25 2019 %o A100318 (Sage) [n for n in (3..100) if (is_prime(n-1) + is_prime(n+1) <= 1)] # _G. C. Greubel_, Apr 24 2019 %Y A100318 Cf. A100317 (exactly one of n-1 and n+1 is prime/composite), A100319. %K A100318 nonn %O A100318 1,1 %A A100318 _Rick L. Shepherd_, Nov 13 2004