A053737 Sum of digits of (n written in base 4).

0, 1, 2, 3, 1, 2, 3, 4, 2, 3, 4, 5, 3, 4, 5, 6, 1, 2, 3, 4, 2, 3, 4, 5, 3, 4, 5, 6, 4, 5, 6, 7, 2, 3, 4, 5, 3, 4, 5, 6, 4, 5, 6, 7, 5, 6, 7, 8, 3, 4, 5, 6, 4, 5, 6, 7, 5, 6, 7, 8, 6, 7, 8, 9, 1, 2, 3, 4, 2, 3, 4, 5, 3, 4, 5, 6, 4, 5, 6, 7, 2, 3, 4, 5, 3, 4, 5, 6, 4, 5, 6, 7, 5, 6, 7, 8, 3, 4, 5, 6, 4, 5, 6, 7, 5

Offset

0,3

Comments

Also the fixed point of the morphism 0->{0,1,2,3}, 1->{1,2,3,4}, 2->{2,3,4,5}, etc. - Robert G. Wilson v, Jul 27 2006

Links

Donovan Johnson, Table of n, a(n) for n = 0..10000

F. T. Adams-Watters and F. Ruskey, Generating Functions for the Digital Sum and Other Digit Counting Sequences, JIS Vol. 12 (2009), Article 09.5.6.

Steve Butler and Ron L. Graham, Shuffling with ordered cards, arXiv 1003:4422 [math.CO], 2010.

Jeffrey O. Shallit, Problem 6450, Advanced Problems, The American Mathematical Monthly, Vol. 91, No. 1 (1984), pp. 59-60; Two series, solution to Problem 6450, ibid., Vol. 92, No. 7 (1985), pp. 513-514.

Robert Walker, Self Similar Sloth Canon Number Sequences.

Eric Weisstein's World of Mathematics, Digit Sum.

Formula

From Benoit Cloitre, Dec 19 2002: (Start)

a(0) = 0, a(4n+i) = a(n)+i for 0 <= i <= 3.

a(n) = n - 3*Sum_{k>0} floor(n/4^k) = n - 3*A054893(n). (End)

G.f.: (Sum_{k>=0} (x^(4^k) + 2*x^(2*4^k) + 3*x^(3*4^k))/(1 + x^(4^k) + x^(2*4^k) + x^(3*4^k))/(1-x). - Franklin T. Adams-Watters, Nov 03 2005

a(n) = A138530(n,4) for n > 3. - Reinhard Zumkeller, Mar 26 2008

a(n) = Sum_{k>=0} A030386(n,k). - Philippe Deléham, Oct 21 2011

a(n) = A007953(A007090(n)). - Reinhard Zumkeller, Mar 19 2015

a(0) = 0; a(n) = a(n - 4^floor(log_4(n))) + 1. - Ilya Gutkovskiy, Aug 23 2019

Sum_{n>=1} a(n)/(n*(n+1)) = 4*log(4)/3 (Shallit, 1984). - Amiram Eldar, Jun 03 2021

Example

a(20) = 1+1+0 = 2 because 20 is written as 110 base 4.
From Omar E. Pol, Feb 21 2010: (Start)
This can be written as a triangle (cf. A000120):
  0,
  1,2,3,
  1,2,3,4,2,3,4,5,3,4,5,6,
  1,2,3,4,2,3,4,5,3,4,5,6,4,5,6,7,2,3,4,5,3,4,5,6,4,5,6,7,5,6,7,8,3,4,5,6,4,5,6,7,5,6,7,8,6,7,8,9,
  1,2,3,4,2,3,4,5,3,4,5,6,4,5,6,7,2,3,4,5,3,4,5,6,4,5,6,7,5,6,7,8,3,4,5,6,4,...
where the rows converge to A173524.
(End)

Maple

A053737 := proc(n)
    add(d, d=convert(n, base, 4)) ;
end proc: # R. J. Mathar, Oct 31 2012

Mathematica

Table[Plus @@ IntegerDigits[n, 4], {n, 0, 100}] (* or *)
Nest[ Flatten[ #1 /. a_Integer -> {a, a+1, a+2, a+3}] &, {0}, 4] (* Robert G. Wilson v, Jul 27 2006 *)
DigitSum[Range[0, 100], 4] (* Paolo Xausa, Aug 01 2024 *)

Prog

(PARI) a(n)=if(n<1, 0, if(n%4, a(n-1)+1, a(n/4)))
(PARI) a(n) = sumdigits(n, 4); \\ Michel Marcus, Aug 24 2019
(Haskell)
a053737 n = if n == 0 then 0 else a053737 m + r where (m, r) = divMod n 4
-- Reinhard Zumkeller, Mar 19 2015
(Magma) [&+Intseq(n, 4):n in [0..104]]; // Marius A. Burtea, Jan 17 2019
(MATLAB) for u=0:104; sol(u+1)=sum(dec2base(u, 4)-'0'); end
sol % Marius A. Burtea, Jan 17 2019

Crossrefs

Cf. A231664-A231667, A138530.

Cf. A173524. - Omar E. Pol, Feb 21 2010

Sum of digits of n written in bases 2-16: A000120, A053735, this sequence, A053824, A053827, A053828, A053829, A053830, A007953, A053831, A053832, A053833, A053834, A053835, A053836.

Related base-4 sequences: A053737, A230631, A230632, A010064, A230633, A230634, A230635, A230636, A230637, A230638, A010065 (trajectory of 1).

Cf. A007090, A239690.

Sequence in context: A007720 A129968 A027615 * A033924 A276328 A276332

Adjacent sequences: A053734 A053735 A053736 * A053738 A053739 A053740

Keyword

base,nonn,easy

Author

Henry Bottomley, Mar 28 2000

Status

approved