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 A164650 #8 Jul 14 2012 11:32:31
%S A164650 679,10127,20273,672203,971261,1133639,1247129,1336231,1646743,
%T A164650 1701089,2369471,2674969,2722499,2989909,3160079,3597659,4545749,
%U A164650 6333503,7127861,9357101,10574629,20070061,52928293,67931137,74731807,79940069,80704813,93444911,128155333
%N A164650 Numbers n such that sigma(n)/phi(n) = 49/36.
%C A164650 A subsequence of A011257.
%C A164650 If 7^{k+1}-1 = d*D such that p = 2*7^{k+1}*(d+1)-1 and q = 2*(7^{k+1}+D)-1 are distinct primes, then n = 7^k*p*q is a term of this sequence.
%C A164650 The same theorem holds for sequences of numbers such that sigma/phi=b^2/(b-1)^2 with other primes b (here b=7), cf. A068390, A164646, A164648.
%H A164650 Donovan Johnson, <a href="/A164650/b164650.txt">Table of n, a(n) for n = 1..1000</a>
%o A164650 (PARI) for( n=1,1e7, sigma(n)==49/36*eulerphi(n) && print1(n","))
%Y A164650 Cf. A000010 (=phi), A000203 (=sigma), A068390 (sigma/phi=4), A163667 (sigma/phi=9), A164646-A164649.
%K A164650 nonn
%O A164650 1,1
%A A164650 _M. F. Hasler_, Aug 22 2009