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%I #25 Jul 09 2017 04:53:05
%S 1,3,6,10,15,21,28,36,45,54,61,66,69,70,69,66,61,54,45,36,28,21,15,10,
%T 6,3,1
%N Number of 3-digit numbers whose digits add up to n.
%C The sequence as a whole is palindromic; a(n) = a(28-n). - _Jon E. Schoenfield_, Nov 19 2016
%F G.f.: (1 - x^10)^2*(x - x^10)/(1 - x)^3. - _Miquel Cerda_, Jul 09 2017
%e a(4) = 10 because there are 10 different 3-digit numbers whose digit sum is 4 (103, 112, 121, 130, 202, 211, 220, 301, 310, 400, which are the 3-digit elements of A052218).
%p for i from 1 to 9*3 do a[i] := 0:od:for i from 100 to 999 dob := convert(i,base,10): s := sum(b[j],j=1..nops(b)):a[s] := a[s]+1:od:seq(a[j],j=1..3*9);
%Y Cf. A071816.
%K fini,full,nonn,base
%O 1,2
%A _Graeme McRae_, Jun 07 2002
%E Corrected and extended by _Sascha Kurz_, Feb 07 2003
%E Name clarified by _Jon E. Schoenfield_, Nov 20 2016
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