A048688 - OEIS

%I #12 May 19 2017 20:28:52

%S 1,2,2,3,3,3,3,4,4,5,5,5,5,6,5,8,6,6,8,9,6,11,7,11,10,10,9,11,11,11,

%T 10,15,13,15,11,15,16,14,14,16,15,15,12,18,17,18,12,22,18,20,19,21,17,

%U 20,19,24,21,21,15,25,19,18,19,24,21,28,25,26,24,29,19,29,25,24,26,29,19

%N Number of classes generated by function A000005 when applied to binomial coefficients.

%H G. C. Greubel, <a href="/A048688/b048688.txt">Table of n, a(n) for n = 1..1000</a>

%F a(n) = length(union(A000005(binomial(n,k)))), for 0<= k <= n.

%e For n=9 A000005({C(9,k)})={1,3,9,12,12,12,12,9,3,1} includes 4 distinct values so generating 4 classes of k values: {0,9},{1,8},{2,7} and {3,4,5,6}. So a(9)=4.

%t Table[Length[Union[Table[DivisorSigma[0, Binomial[n, k]], {k, 0, n}]]], {n, 1, 50}] (* _G. C. Greubel_, May 19 2017 *)

%Y Cf. A000005, A001221, A007947.

%K nonn

%O 1,2

%A _Labos Elemer_