A132066 - OEIS

%I #11 Oct 30 2019 16:50:35

%S 1,1,1,1,2,1,1,2,1,4,1,1,1,3,1,6,1,1,2,4,1,2,6,1,1,3,5,1,10,1,1,1,1,2,

%T 6,1,12,1,1,5,7,1,2,2,10,1,1,2,4,8,1,16,1,1,1,3,3,9,1,18,1,1,2,1,5,10,

%U 1,2,4,14,1,1,9,11,1,22,1,1,1,1,2,2,4,12,1,4,20,1,1,11,13,1,2,6,18,1,1,2,3

%N Irregular array: the sum of the first m terms of row n is the m-th positive divisor of n.

%C Row n contains A000005(n) terms.

%e The positive divisors of 20 are 1,2,4,5,10,20. Row 20 of the array is 1,1,2,1,5,10. So we have 1=1; 1+1=2; 1+1+2=4; 1+1+2+1=5; 1+1+2+1+5=10; 1+1+2+1+5+10=20.

%e The first 10 rows:

%e 1;

%e 1,1;

%e 1,2;

%e 1,1,2;

%e 1,4;

%e 1,1,1,3

%e 1,6;

%e 1,1,2,4;

%e 1,2,6;

%e 1,1,3,5

%t f[n_] := Block[{d},d = Divisors[n]; d - Prepend[Most[d], 0]]; Flatten[Array[f, 40]] (* _Ray Chandler_, Nov 01 2007 *)

%Y Cf. A027750, A000005.

%K nonn,tabf

%O 1,5

%A _Leroy Quet_, Oct 30 2007

%E Extended by _Ray Chandler_, Nov 01 2007