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A361438 Triangle T(n,k), n >= 1, 1 <= k <= A046801(n), read by rows, where T(n,k) is k-th smallest divisor of 2^n-1.

%I A361438 #34 Oct 20 2024 17:42:33
%S A361438 1,1,3,1,7,1,3,5,15,1,31,1,3,7,9,21,63,1,127,1,3,5,15,17,51,85,255,1,
%T A361438 7,73,511,1,3,11,31,33,93,341,1023,1,23,89,2047,1,3,5,7,9,13,15,21,35,
%U A361438 39,45,63,65,91,105,117,195,273,315,455,585,819,1365,4095,1,8191,1,3,43,127,129,381,5461,16383
%N A361438 Triangle T(n,k), n >= 1, 1 <= k <= A046801(n), read by rows, where T(n,k) is k-th smallest divisor of 2^n-1.
%H A361438 Seiichi Manyama, <a href="/A361438/b361438.txt">Rows n = 1..64, flattened</a>
%H A361438 <a href="/index/Di#divisors">Index entries for sequences related to divisors of numbers</a>
%e A361438 Triangle begins:
%e A361438   1;
%e A361438   1,   3;
%e A361438   1,   7;
%e A361438   1,   3,  5,   15;
%e A361438   1,  31;
%e A361438   1,   3,  7,    9, 21, 63;
%e A361438   1, 127;
%e A361438   1,   3,  5,   15, 17, 51,  85,  255;
%e A361438   1,   7, 73,  511;
%e A361438   1,   3, 11,   31, 33, 93, 341, 1023;
%e A361438   1,  23, 89, 2047;
%p A361438 T:= n-> sort([numtheory[divisors](2^n-1)[]])[]:
%p A361438 seq(T(n), n=1..12);  # _Alois P. Heinz_, Oct 20 2024
%t A361438 Divisors[2^Range[15] - 1] (* _Paolo Xausa_, Jul 02 2024 *)
%Y A361438 Subsequence of A027750.
%Y A361438 Cf. A000225, A049479 (2nd column), A075708 (row sums).
%Y A361438 Cf. A374237 (analogous for 2^n + 1).
%K A361438 nonn,tabf,look
%O A361438 1,3
%A A361438 _Seiichi Manyama_, Mar 12 2023