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A099034 a(n) = Sum_{k=1..n} (-1)^A000120(5*k). 1
1, 2, 3, 4, 3, 4, 3, 4, 5, 4, 3, 4, 5, 4, 5, 6, 7, 8, 9, 8, 9, 8, 7, 8, 9, 10, 11, 10, 9, 10, 9, 10, 11, 12, 13, 14, 13, 14, 15, 14, 13, 14, 15, 14, 15, 14, 15, 16, 17, 18, 19, 20, 19, 20, 21, 20, 19, 18, 17, 18, 19, 18, 19, 20, 21, 22, 23, 24, 23, 24, 23, 24, 25, 24, 23 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(n) is of order n^(log(5)/log(16)).

LINKS

Gheorghe Coserea, Table of n, a(n) for n = 1..65536

P. J. Grabner, A note on the parity of the sum-of-digits function, Séminaire Lotharingien de Combinatoire, B30e (1993), 8 pp.

FORMULA

a(2*16^n) = 2*5^n, a(4*16^n) = a(8*16^n) = 4*5^n, a(16^(n+1)) = 6*5^n. - Gheorghe Coserea, Dec 03 2016

PROG

(PARI) a(n) = sum(k=1, n, (-1)^hammingweight(5*k));

(PARI)

seq(N) = {

  my(v = vector(N), w=0); v[1] = 1;

  for (k = 2, N, w = hammingweight(5*k)%2; v[k] = v[k-1] + 1-2*w);

  v;

};

seq(75) \\ Gheorghe Coserea, Dec 03 2016

CROSSREFS

Cf. A046820, A099033.

Sequence in context: A123709 A165482 A323242 * A165576 A304730 A323374

Adjacent sequences:  A099031 A099032 A099033 * A099035 A099036 A099037

KEYWORD

nonn,base

AUTHOR

Ralf Stephan, Sep 27 2004

EXTENSIONS

Name corrected by Michel Marcus, Dec 03 2016

STATUS

approved

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Last modified November 18 03:48 EST 2019. Contains 329248 sequences. (Running on oeis4.)