A361438 - OEIS

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.

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, 7, 73, 511, 1, 3, 11, 31, 33, 93, 341, 1023, 1, 23, 89, 2047, 1, 3, 5, 7, 9, 13, 15, 21, 35, 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

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,3

LINKS

Seiichi Manyama, Rows n = 1..64, flattened

Index entries for sequences related to divisors of numbers

EXAMPLE

Triangle begins:

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, 7, 73, 511;

1, 3, 11, 31, 33, 93, 341, 1023;

1, 23, 89, 2047;

MAPLE

T:= n-> sort([numtheory[divisors](2^n-1)[]])[]:

seq(T(n), n=1..12); # Alois P. Heinz, Oct 20 2024

MATHEMATICA

Divisors[2^Range[15] - 1] (* Paolo Xausa, Jul 02 2024 *)

CROSSREFS

Subsequence of A027750.

Cf. A000225, A049479 (2nd column), A075708 (row sums).

Cf. A374237 (analogous for 2^n + 1).

Sequence in context: A038712 A354587 A065745 * A268670 A360331 A227873

Adjacent sequences: A361435 A361436 A361437 * A361439 A361440 A361441

KEYWORD

nonn,tabf,look

AUTHOR

Seiichi Manyama, Mar 12 2023

STATUS

approved