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 A063446 #37 Mar 08 2025 06:00:22
%S A063446 1,5,7,13,37,39,49,55,61,65,69,73,77,87,129,134,157,183,185,193,194,
%T A063446 221,237,247,249,254,265,275,277,295,309,313,321,327,343,363,365,397,
%U A063446 398,417,421,437,454,455,457,458,469,471,473,475,482,493,497,505,517
%N A063446 Integers m such that d(m+1) = 2*d(m), where d(m) = A000005(m).
%H A063446 Amiram Eldar, <a href="/A063446/b063446.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..1000 from Harry J. Smith)
%e A063446 For m = 77, 2*d(77) = 2*4 = 8 = d(78).
%t A063446 Select[Range@ 520, DivisorSigma[0, # + 1] == 2 DivisorSigma[0, #] &] (* _Michael De Vlieger_, Feb 19 2017 *)
%o A063446 (PARI) { n=0; for (m=1, 10^9, if (numdiv(m + 1) == 2*numdiv(m), write("b063446.txt", n++, " ", m); if (n==1000, break)) ) } \\ _Harry J. Smith_, Aug 21 2009
%o A063446 (Magma) [n: n in [1..600] | NumberOfDivisors(n+1) eq (2* NumberOfDivisors(n))]; // _Vincenzo Librandi_, Aug 04 2018
%o A063446 (GAP) Filtered([1..520],n->Tau(n+1)=2*Tau(n)); # _Muniru A Asiru_, Aug 20 2018
%Y A063446 Cf. A000005, A063449, A063450.
%K A063446 nonn
%O A063446 1,2
%A A063446 _Labos Elemer_, Jul 24 2001