A191973 - OEIS

%I #14 Mar 31 2012 13:22:30

%S 1,2,1,2,3,4,6,2,3,4,6,12,2,3,4,5,6,8,12,20,4,5,6,10,30,2,3,4,5,6,7,8,

%T 9,10,12,15,18,24,42,6,7,8,14,56,4,6,7,8,9,10,12,16,24,40,72,6,8,9,10,

%U 12,18,36,90,5,6,8,9,10,11,12,14,15,20,30,35,60

%N Irregular triangle read by rows: row n consists of n and the positive integers m where m-n divides m*n.

%C The maximum term of the n-th row is n*(n+1). The minimum term of the n-th row seems to be A063428(n) if n>=2. The length of row n is A146564(n) + 1.

%H Nathaniel Johnston, <a href="/A191973/b191973.txt">Rows 1..250, flattened</a>

%e The triangle begins:

%e 1 2

%e 1 2 3 4  6

%e 2 3 4 6  12

%e 2 3 4 5  6  8  12 20

%e 4 5 6 10 30

%e 2 3 4 5  6  7  8  9  10 12 15 18 24 42

%e 6 7 8 14 56

%e ...

%p for n from 1 to 10 do for m from 1 to n*(n+1) do if(n=m or m*n mod (m-n) = 0)then printf("%d, ",m): fi: od: od:

%Y Cf. A162821 (row 30), A162822 (row 36), A162823 (row 42), A162824 (row 48), A162825 (row 60), A127730.

%K nonn,easy,tabf

%O 1,2

%A _Nathaniel Johnston_, Jun 22 2011