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 A138303 #18 Jun 06 2025 14:47:53
%S A138303 3,15,495,624,1308,1365,1494,1659,1848,6363,8064,12780,13908,14013,
%T A138303 16530,18018,18654,28575,30885,31020,38130,43674,48735,50379,57198,
%U A138303 60915,61059,62943,75768,76359,76569,80949,81075,83028,84045,86085,88185,104664,105588
%N A138303 Numbers k such that k*(k+1)-1 and k*(k+1)+1 are twin primes and k*(k+3)-1 and k*(k+3)+1 are also twin primes.
%H A138303 David A. Corneth, <a href="/A138303/b138303.txt">Table of n, a(n) for n = 1..10000</a> (first 500 terms from Pierre CAMI)
%e A138303 3*4=12: 11 and 13 are twin primes; 3*6=18 and 17 and 19 are also twin primes.
%t A138303 Select[Range[106000],AllTrue[{#*(#+1)-1,#*(#+1)+1,#*(#+3)-1,#*(#+3)+1},PrimeQ]&] (* _James C. McMahon_, Jun 06 2025 *)
%o A138303 (PARI) isok(n) = isprime(n*(n+1)-1) && isprime(n*(n+1)+1) && isprime(n*(n+3)-1) && isprime(n*(n+3)+1); \\ _Michel Marcus_, Sep 23 2019
%Y A138303 Subsequence of A088485.
%K A138303 nonn
%O A138303 1,1
%A A138303 _Pierre CAMI_, Mar 13 2008