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A374237 Irregular triangle read by rows where row n lists, in increasing order, the divisors of 2^n + 1.

%I A374237 #25 Oct 20 2024 17:45:46
%S A374237 1,2,1,3,1,5,1,3,9,1,17,1,3,11,33,1,5,13,65,1,3,43,129,1,257,1,3,9,19,
%T A374237 27,57,171,513,1,5,25,41,205,1025,1,3,683,2049,1,17,241,4097,1,3,2731,
%U A374237 8193,1,5,29,113,145,565,3277,16385,1,3,9,11,33,99,331,993,2979,3641,10923,32769
%N A374237 Irregular triangle read by rows where row n lists, in increasing order, the divisors of 2^n + 1.
%H A374237 Paolo Xausa, <a href="/A374237/b374237.txt">Table of n, a(n) for n = 0..11484</a> (rows 0..135 of the triangle, flattened).
%H A374237 <a href="/index/Di#divisors">Index entries for sequences related to divisors of numbers</a>
%e A374237 Triangle begins:
%e A374237    [0]  1,   2;
%e A374237    [1]  1,   3;
%e A374237    [2]  1,   5;
%e A374237    [3]  1,   3,  9;
%e A374237    [4]  1,  17;
%e A374237    [5]  1,   3, 11,  33;
%e A374237    [6]  1,   5, 13,  65;
%e A374237    [7]  1,   3, 43, 129;
%e A374237    [8]  1, 257;
%e A374237    [9]  1,   3,  9,  19,  27,   57, 171, 513;
%e A374237   [10]  1,   5, 25,  41, 205, 1025;
%e A374237   ...
%p A374237 T:= n-> sort([numtheory[divisors](2^n+1)[]])[]:
%p A374237 seq(T(n), n=0..15);  # _Alois P. Heinz_, Oct 20 2024
%t A374237 Divisors[2^Range[0, 20] + 1]
%Y A374237 Subsequence of A027750.
%Y A374237 Cf. A000051, A002586 (2nd column), A046798 (row lengths), A069060 (row products), A069061 (row sums).
%Y A374237 Cf. A361438 (analogous for 2^n - 1).
%K A374237 nonn,tabf,look
%O A374237 0,2
%A A374237 _Paolo Xausa_, Jul 02 2024