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Numbers with at least two pairs of distinct divisors having equal differences.
4

%I #9 Aug 26 2015 12:42:55

%S 6,12,15,18,20,24,28,30,36,40,42,45,48,54,56,60,63,66,70,72,75,78,80,

%T 84,88,90,91,96,99,100,102,105,108,110,112,114,120,126,130,132,135,

%U 138,140,144,150,153,156,160,162,165,168,174,176,180,182,186,189,190,192,195

%N Numbers with at least two pairs of distinct divisors having equal differences.

%C A129510(a(n)) < A066446(a(n)).

%H Reinhard Zumkeller, <a href="/A129512/b129512.txt">Table of n, a(n) for n = 1..10000</a>

%e See example for a(12)=45 in A129510.

%o (Haskell)

%o import Data.List.Ordered (minus)

%o a129512 n = a129512_list !! (n-1)

%o a129512_list = minus [1..] a129511_list

%o -- _Reinhard Zumkeller_, Aug 10 2015

%o (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 Cf. A129510, A066446, A129511 (complement).

%Y Subsequences: A008588, A008597, A129521, A259366.

%K nonn

%O 1,1

%A _Reinhard Zumkeller_, Apr 19 2007