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 A063964 #18 Aug 18 2019 04:34:02
%S A063964 11,14,224,957,1334,1634,2685,9347,13915,16260,20145,20335,33998,
%T A063964 37236,42251,42818,51624,55308,56419,56975,71874,74918,77748,79824,
%U A063964 79826,79833,84134,93632,106600,111506,120680,122073,138237,142116,147454
%N A063964 Numbers k such that k and k+1 have the same sum of squarefree divisors, or sqf(k) = sqf(k+1), where sqf(k) = A048250(k).
%H A063964 Amiram Eldar, <a href="/A063964/b063964.txt">Table of n, a(n) for n = 1..1000</a> (terms 1..170 from Harry J. Smith)
%t A063964 sqs[n_] := Times@@(1 + FactorInteger[n][[;; , 1]]); seq={}; s1 = 1; Do[s2 = sqs[n]; If[s2 == s1, AppendTo[seq, n-1]]; s1 = s2, {n, 2, 10^5}]; seq (* _Amiram Eldar_, Aug 18 2019 *)
%o A063964 (PARI) sqf(n) = sumdiv(n,d, if(issquarefree(d),d,0)); for(n=1,10^7, if(sqf(n)==sqf(n+1),print(n)))
%o A063964 (PARI) { n=0; s=0; for (m=1, 10^9, t=sumdiv(m + 1, d, if(issquarefree(d), d, 0)); if(s==t, write("b063964.txt", n++, " ", m); if (n==170, break)); s=t ) } \\ _Harry J. Smith_, Sep 04 2009
%Y A063964 Cf. A048250.
%K A063964 easy,nonn
%O A063964 1,1
%A A063964 _Jason Earls_, Sep 04 2001