

A071817


Number of 3digit numbers whose digits add up to n.


10



1, 3, 6, 10, 15, 21, 28, 36, 45, 54, 61, 66, 69, 70, 69, 66, 61, 54, 45, 36, 28, 21, 15, 10, 6, 3, 1
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OFFSET

1,2


COMMENTS

The sequence as a whole is palindromic; a(n) = a(28n).  Jon E. Schoenfield, Nov 19 2016


LINKS

Table of n, a(n) for n=1..27.


FORMULA

G.f.: (1  x^10)^2*(x  x^10)/(1  x)^3.  Miquel Cerda, Jul 09 2017


EXAMPLE

a(4) = 10 because there are 10 different 3digit numbers whose digit sum is 4 (103, 112, 121, 130, 202, 211, 220, 301, 310, 400, which are the 3digit elements of A052218).


MAPLE

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);


CROSSREFS

Cf. A071816.
Sequence in context: A037123 A062918 A113168 * A033442 A105335 A130489
Adjacent sequences: A071814 A071815 A071816 * A071818 A071819 A071820


KEYWORD

fini,full,nonn,base


AUTHOR

Graeme McRae, Jun 07 2002


EXTENSIONS

Corrected and extended by Sascha Kurz, Feb 07 2003
Name clarified by Jon E. Schoenfield, Nov 20 2016


STATUS

approved



