login
A374237
Irregular triangle read by rows where row n lists, in increasing order, the divisors of 2^n + 1.
3
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, 27, 57, 171, 513, 1, 5, 25, 41, 205, 1025, 1, 3, 683, 2049, 1, 17, 241, 4097, 1, 3, 2731, 8193, 1, 5, 29, 113, 145, 565, 3277, 16385, 1, 3, 9, 11, 33, 99, 331, 993, 2979, 3641, 10923, 32769
OFFSET
0,2
LINKS
EXAMPLE
Triangle begins:
[0] 1, 2;
[1] 1, 3;
[2] 1, 5;
[3] 1, 3, 9;
[4] 1, 17;
[5] 1, 3, 11, 33;
[6] 1, 5, 13, 65;
[7] 1, 3, 43, 129;
[8] 1, 257;
[9] 1, 3, 9, 19, 27, 57, 171, 513;
[10] 1, 5, 25, 41, 205, 1025;
...
MAPLE
T:= n-> sort([numtheory[divisors](2^n+1)[]])[]:
seq(T(n), n=0..15); # Alois P. Heinz, Oct 20 2024
MATHEMATICA
Divisors[2^Range[0, 20] + 1]
CROSSREFS
Subsequence of A027750.
Cf. A000051, A002586 (2nd column), A046798 (row lengths), A069060 (row products), A069061 (row sums).
Cf. A361438 (analogous for 2^n - 1).
Sequence in context: A353467 A168008 A178810 * A319627 A334990 A217668
KEYWORD
nonn,tabf,look
AUTHOR
Paolo Xausa, Jul 02 2024
STATUS
approved