A181415 - OEIS

%I #10 May 17 2016 08:31:41

%S 1,1,1,1,6,2,1,12,9,36,6,1,20,40,120,180,240,24,1,30,75,50,300,1200,

%T 300,1200,2700,1800,120,1,42,126,210,630,3150,2100,3150,4200,25200,

%U 12600,12600,37800,15120,720,1,56,196,392,245,1176,7056,11760,8820,11760,11760,88200

%N Irregular triangle a(n,k) = A049009(n,k)/n, read by rows 1<=k<=A000041(n).

%F Sum_{k=1.. A000041(n)} a(n,k) = A000169(n). (Row sums)

%F a(n,k) = A098546(n,k) *A049019(n,k) /n. - Compare with the formula in A101818.

%e Row three is calculated as follows:

%e ( 3 18 6) divided by (3 3 3) yielding (1 6 2)

%e 1;

%e 1,1;

%e 1,6,2;

%e 1,12,9,36,6;

%e 1,20,40,120,180,240,24;

%e 1,30,75,50,300,1200,300,1200,2700,1800,120;

%e 1,42,126,210,630,3150,2100,3150,4200,25200,12600,12600,37800,15120,720;

%Y Cf. A000169 (row sums), A000081 (unlabeled rooted trees) A179438 (a similar refinement), A054589, A135278, A019538, A101817, A101818

%K nonn,tabf

%O 1,5

%A _Alford Arnold_, Oct 20 2010

%E Edited by _R. J. Mathar_, May 17 2016