A393397 - OEIS

%I #10 Feb 18 2026 15:46:29

%S 1,2,1,3,1,4,4,1,5,1,6,9,8,1,7,1,8,16,16,1,9,27,1,10,25,32,1,11,1,12,

%T 36,64,81,64,1,13,1,14,49,128,1,15,125,243,1,16,64,256,256,1,17,1,18,

%U 81,216,729,512,1,19,1,20,100,625,1024,1024,1,21,343,2187,1,22,121,2048,1

%N Irregular triangle read by rows: the n-th row gives the list of (n/d)^d where d is a divisor of n.

%H Stefano Spezia, <a href="/A393397/b393397.txt">Table of n, a(n) for n = 1..9534</a> (first 1300 rows of the triangle)

%e The irregular triangle begins as:

%e    1;

%e    2,  1;

%e    3,  1;

%e    4,  4,  1;

%e    5,  1;

%e    6,  9,  8, 1;

%e    7,  1;

%e    8, 16, 16, 1;

%e    9, 27,  1;

%e   10, 25, 32, 1;

%e   11,  1;

%e   12, 36, 64, 81, 64, 1;

%e   ...

%t row[n_]:=Table[(n/d)^d,{d,Divisors[n]}]; Array[row,22]//Flatten

%Y Cf. A000005 (row lengths), A000027 (1st column), A055225 (row sums), A027750, A393227, A393396.

%K nonn,easy,look,tabf

%O 1,2

%A _Stefano Spezia_, Feb 13 2026