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 A061638 #28 Aug 28 2020 06:17:25
%S A061638 29,43,71,113,127,197,211,281,337,379,421,449,491,631,673,701,757,883,
%T A061638 1009,1051,1373,1471,2017,2269,2521,2647,2689,2801,3137,3361,3529,
%U A061638 4201,4481,5881,6301,7001,7057,7351,7561,7841,8233,8821,10501,10753,12097
%N A061638 Primes p such that the greatest prime divisor of p-1 is 7.
%C A061638 Prime numbers n for which cos(2*Pi/n) is an algebraic number of 7th degree. - _Artur Jasinski_, Dec 13 2006
%H A061638 Harry J. Smith and Charles R Greathouse IV, <a href="/A061638/b061638.txt">Table of n, a(n) for n = 1..10000</a> (first 500 terms from Smith)
%F A061638 Primes of form 2^a*3^b*5^c*7^d + 1 with a and d > 1.
%e A061638 For n = {4, 8, 9, 12}, a(n)-1 = {70, 210, 280, 420} = 7*{10, 30, 40, 60}.
%t A061638 Select[Prime[Range[2000]],FactorInteger[#-1][[-1,1]] ==7&] (* _Harvey P. Dale_, Mar 12 2011 *)
%o A061638 (PARI) default(primelimit, 108864001); n=0; forprime (p=3, 108864001, f=factor(p - 1)~; if (f[1, length(f)]==7, write("b061638.txt", n++, " ", p))) \\ _Harry J. Smith_, Jul 25 2009
%o A061638 (PARI) list(lim)=my(v=List(), t, t5, t7); lim\=1; lim--; for(a=1, logint(lim\2, 7), t7=2*7^a; for(b=0, logint(lim\t7, 5), t5=5^b*t7; for(c=0, logint(lim\t5, 3), t=3^c*t5; while(t<=lim, if(isprime(t+1), listput(v, t+1)); t<<=1)))); Set(v) \\ _Charles R Greathouse IV_, Oct 29 2018
%Y A061638 The 4th in a family of sequences after A019434(=Fermat-primes), A058383, A061599.
%Y A061638 Cf. A019434, A058383, A023503, A034694, A006530, A006093, A035095, A061599.
%Y A061638 Cf. A004729, A058383, A125867-A125875, A024899.
%K A061638 nonn
%O A061638 1,1
%A A061638 _Labos Elemer_, Jun 13 2001