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 A217442 #35 Feb 16 2020 20:44:18
%S A217442 1,2,3,4,6,24,28,30,32,36,45,48,56,64,66,72,76,80,92,96,102,104,120,
%T A217442 126,128,144,168,176,180,184,186,192,200,208,228,236,240,248,252,256,
%U A217442 270,280,288,292,304,312,320,328,336,352,360,364,376,384,420,424,426
%N A217442 Numbers n such that d(prime(n) - 1) | n, where d(k) is the number of divisors of k.
%C A217442 For n in {1,2,3,4,6}, n = d(prime(n)-1). There are no others with this property, as conjectured by _Raphie Frank_ and proved by _Charles R Greathouse IV_ on Physics Forums (Nov, 2010).
%H A217442 T. D. Noe, <a href="/A217442/b217442.txt">Table of n, a(n) for n = 1..1000</a>
%H A217442 Physics Forums, <a href="http://www.physicsforums.com/showthread.php?t=442527">Prime Indices & the Divisors of (p'_n - 1): A Lattice-Related Question</a> , Nov 2010
%e A217442 d(701 - 1)*7 = pi(701) = 126. The 126th prime is 701 and d(701 - 1) = 18; 18 divides 126 (7 times), so 126 is a member of this sequence.
%t A217442 Select[Range[352], Mod[#, DivisorSigma[0, Prime[#] - 1]] == 0 &] (* _T. D. Noe_, Oct 11 2012 *)
%o A217442 (PARI) is(n)=n%numdiv(prime(n)-1)==0 \\ _Charles R Greathouse IV_, Oct 09 2012
%Y A217442 Cf. A008328.
%K A217442 nonn
%O A217442 1,2
%A A217442 _Raphie Frank_, Oct 04 2012
%E A217442 a(12), a(31), a(39) from _Charles R Greathouse IV_, Oct 09 2012