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A285120 Min(|d(k+1-i) - d(i)|, for i = 1..k, where d(1),..,d(k) are the divisors of n(n+1)/2. 1

%I

%S 0,2,1,3,2,4,3,0,4,6,5,7,6,8,2,9,8,10,9,1,10,12,11,5,12,14,3,15,14,16,

%T 15,2,16,18,9,19,18,20,4,21,20,22,21,3,22,24,23,14,0,26,5,27,26,12,9,

%U 4,28,30,29,31,30,32,6,12,16,34,33,5,34,36,35,37

%N Min(|d(k+1-i) - d(i)|, for i = 1..k, where d(1),..,d(k) are the divisors of n(n+1)/2.

%H Clark Kimberling, <a href="/A285120/b285120.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n)=A056737(A000217(n)).

%e 7(7+1)/2 = 28 has divisors 1,2,4,7,14,28, so that k=6 and d(k+1-i) - d(i) ranges through {-27,-12,-3,3,12,27}, so that a(7) = 3.

%t f[n_] := f[n] = n(n+1)/2;

%t Table[Divisors[f[n]] - Reverse[Divisors[f[n]]], {n, 1, 10}]

%t Table[Min[Abs[Divisors[f[n]] - Reverse[Divisors[f[n]]]]], {n, 1, 100}]

%Y Cf. A000217, A002378, A056737.

%K nonn,easy

%O 1,2

%A _Clark Kimberling_, Apr 11 2017

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Last modified August 9 18:32 EDT 2020. Contains 336326 sequences. (Running on oeis4.)