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 A272600 #23 Feb 26 2024 15:43:07
%S A272600 9,21,25,33,49,55,65,81,85,121,129,145,161,169,201,217,221,253,273,
%T A272600 289,295,301,321,325,343,361,385,441,469,481,501,505,513,545,589,625,
%U A272600 649,685,721,781,801,817,841,865,901,961,973,1001,1025,1027,1081,1089,1101,1135,1177,1261,1281,1333,1345,1369,1405,1441,1501
%N A272600 Composites k such that p-1 divides k-1 for each prime divisor of k-1.
%C A272600 Composites not in A272601.
%H A272600 Charles R Greathouse IV, <a href="/A272600/b272600.txt">Table of n, a(n) for n = 1..10000</a>
%t A272600 pdkQ[n_]:=Module[{p=FactorInteger[n-1][[;;,1]]-1},AllTrue[(n-1)/p,IntegerQ]]; Select[Range[ 1550],CompositeQ[#]&&pdkQ[#]&] (* _Harvey P. Dale_, Feb 26 2024 *)
%o A272600 (PARI) forcomposite(n=4, 10^4, my(q=1, f=factor(n-1)[,1]); for(j=1, #f, if((n-1)%(f[j]-1), q=0; break)); if(q, print1(n,", ") ) );
%o A272600 (PARI) is(n)=my(f=factor(n-1)[,1]); for(i=1,#f, if((n-1)%(f[i]-1), return(0))); !isprime(n) && n>1 \\ _Charles R Greathouse IV_, May 16 2016
%Y A272600 Cf. A080062 (composite n such that p-1 divides n-1 for each prime divisor of n).
%K A272600 nonn
%O A272600 1,1
%A A272600 _Joerg Arndt_, May 16 2016