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 A129512 #13 Jan 27 2025 02:23:06
%S A129512 6,12,15,18,20,24,28,30,36,40,42,45,48,54,56,60,63,66,70,72,75,78,80,
%T A129512 84,88,90,91,96,99,100,102,105,108,110,112,114,120,126,130,132,135,
%U A129512 138,140,144,150,153,156,160,162,165,168,174,176,180,182,186,189,190,192,195
%N A129512 Numbers with at least two pairs of distinct divisors having equal differences.
%H A129512 Reinhard Zumkeller, <a href="/A129512/b129512.txt">Table of n, a(n) for n = 1..10000</a>
%F A129512 A129510(a(n)) < A066446(a(n)).
%e A129512 See example for a(12) = 45 in A129510.
%t A129512 q[k_] := Count[Tally[Differences /@ Subsets[Divisors[k], {2}] // Flatten][[;; , 2]], _?(# > 1 &)] > 0; Select[Range[200], q] (* _Amiram Eldar_, Jan 27 2025 *)
%o A129512 (Haskell)
%o A129512 import Data.List.Ordered (minus)
%o A129512 a129512 n = a129512_list !! (n-1)
%o A129512 a129512_list = minus [1..] a129511_list
%o A129512 -- _Reinhard Zumkeller_, Aug 10 2015
%o A129512 (PARI) is(n)=my(d=divisors(n)); for(i=1,#d-2, for(j=i+1,#d-1, for(k=1,#d, if(i!=k && setsearch(d, d[j]-d[i]+d[k]), return(1))))); 0 \\ _Charles R Greathouse IV_, Aug 26 2015
%Y A129512 Cf. A129510, A066446, A129511 (complement).
%Y A129512 Subsequences: A008588, A008597, A129521, A259366.
%K A129512 nonn
%O A129512 1,1
%A A129512 _Reinhard Zumkeller_, Apr 19 2007