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 A166546 #24 Sep 08 2022 08:45:48
%S A166546 1,2,3,5,6,7,8,10,11,12,13,14,15,17,18,19,20,21,22,23,26,27,28,29,31,
%T A166546 32,33,34,35,37,38,39,41,43,44,45,46,47,48,50,51,52,53,55,57,58,59,60,
%U A166546 61,62,63,65,67,68,69,71,72,73,74,75,76,77,79,80,82,83,84,85,86,87,89,90
%N A166546 Natural numbers n such that d(n) + 1 is prime.
%C A166546 Natural numbers n such that d(d(n)+1)= 2. - _Giovanni Teofilatto_, Oct 26 2009
%C A166546 The complement is the union of A001248, A030514, A030516, A030626, A030627, A030629, A030631, A030632, A030633 etc. - _R. J. Mathar_, Oct 26 2009
%H A166546 Vincenzo Librandi, <a href="/A166546/b166546.txt">Table of n, a(n) for n = 1..6955</a>
%F A166546 {1} U A000040 U A030513 U A030515 U A030628 U A030630 U A030634 U A030636 U A137485 U A137491 U A137493 U ... . - _R. J. Mathar_, Oct 26 2009
%t A166546 Select[Range@90, PrimeQ[DivisorSigma[0, #] + 1] &] (* _Vincenzo Librandi_, Jan 20 2019 *)
%o A166546 (PARI) isok(n) = isprime(numdiv(n)+1); \\ _Michel Marcus_, Jan 20 2019
%o A166546 (Magma) [n: n in [1..100] | IsPrime(NumberOfDivisors(n)+1)]; // _Vincenzo Librandi_, Jan 20 2019
%Y A166546 Cf. A000005.
%Y A166546 Cf. A073915. - _R. J. Mathar_, Oct 26 2009
%K A166546 nonn
%O A166546 1,2
%A A166546 _Giovanni Teofilatto_, Oct 16 2009