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A138471 Number of numbers less than n having the same sum of digits. 5
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 2, 2, 2, 2, 2, 2, 2, 2, 1, 0, 3, 3, 3, 3, 3, 3, 3, 2, 1, 0, 4, 4, 4, 4, 4, 4, 3, 2, 1, 0, 5, 5, 5, 5, 5, 4, 3, 2, 1, 0, 6, 6, 6, 6, 5, 4, 3, 2, 1, 0, 7, 7, 7, 6, 5, 4, 3, 2, 1, 0, 8, 8, 7, 6, 5, 4, 3, 2, 1, 0, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0, 2, 3, 4, 5, 6 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,21

COMMENTS

A138470(n) + a(n) + A138472(n) = n;

a(A051885(n)) = 0.

a(A228915(n)) = a(n)+1. - Robert Israel, May 26 2017

LINKS

Robert Israel, Table of n, a(n) for n = 0..10000 (terms 0..1500 from Reinhard Zumkeller)

Index entries for Colombian or self numbers and related sequences

EXAMPLE

a(42)=#{6,15,24,33}=4.

MAPLE

N:= 1000: # to get a(0) to a(N)

C:= Vector(9*(1+ilog10(N))):

A[0]:= 0:

for n from 1 to N do

  s:= convert(convert(n, base, 10), `+`);

  A[n]:= C[s];

  C[s]:= C[s]+1;

od:

seq(A[i], i=0..N); # Robert Israel, May 25 2017

MATHEMATICA

Module[{nn=110, sd}, sd=Total[IntegerDigits[#]]&/@Range[nn]; Join[{0}, Table[ Count[Take[sd, i-1], sd[[i]]], {i, nn}]]] (* Harvey P. Dale, Aug 14 2013 *)

PROG

(PARI) a(n) = my(sdn=sumdigits(n)); sum(k=1, n-1, sumdigits(k) == sdn); \\ Michel Marcus, May 26 2017

CROSSREFS

Cf. A007953, A051885, A138470, A138472, A228915.

Sequence in context: A263204 A194322 A052010 * A102669 A248327 A055098

Adjacent sequences:  A138468 A138469 A138470 * A138472 A138473 A138474

KEYWORD

nonn,base,look

AUTHOR

Reinhard Zumkeller, Mar 19 2008

STATUS

approved

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Last modified August 19 07:12 EDT 2017. Contains 290794 sequences.