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%I #15 Jul 04 2017 09:25:32
%S 1,9,45,165,495,1287,3003,6435,12870,24309,43741,75465,125445,201675,
%T 314523,477015,705012,1017225,1435005,1981845,2682559,3562131,4644255,
%U 5949615,7493982,9286233,11326425,13604085,16096905,18770031,21576079,24455955,27340500,30152925,32811945,35235465,37344615,39067875,40344975,41130255,41395240,41130255,40344975,39067875,37344615,35235465,32811945,30152925,27340500,24455955,21576079,18770031,16096905,13604085,11326425,9286233,7493982,5949615,4644255,3562131,2682559,1981845,1435005,1017225,705012,477015,314523,201675,125445,75465,43741,24309,12870,6432,3003,1287,495,165,45,9,1
%N Number of 9-digit numbers whose sum of digits is n.
%C There are 900000000 numbers with 9 decimal digits, the smallest being 100000000 and the largest 999999999.
%H Miquel Cerda, <a href="/A289354/b289354.txt">Table of n, a(n) for n = 1..81</a>
%F a(n) = a(82 - n). - _David A. Corneth_, Jul 03 2017
%F G.f.: (x - x^10)/(1 - x)*((1 - x^10)/(1 - x))^8 - _Michael De Vlieger_, Jul 04 2017
%e a(2)=9: 100000001, 100000010, 100000100, 100001000, 100010000, 100100000, 101000000, 11000000, 20000000.
%t With[{d = 9}, Rest@ CoefficientList[Series[(x - x^10)/(1 - x) ((1 - x^10)/(1 - x))^(d - 1), {x, 0, 9 d}], x]] (* _Michael De Vlieger_, Jul 04 2017 *)
%Y Cf. A071817 (3-digit numbers), A090579 (4-digit numbers), A090580 (5-digit numbers), A090581 (6-digit numbers), A278969 (7-digit numbers), A278971 (8-digit numbers).
%K base,fini,full,nonn
%O 1,2
%A _Miquel Cerda_, Jul 03 2017
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