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A298639 Numbers k such that the digital sum of k and the digital root of k have the same parity. 2
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 20, 21, 22, 23, 24, 25, 26, 27, 30, 31, 32, 33, 34, 35, 36, 40, 41, 42, 43, 44, 45, 50, 51, 52, 53, 54, 60, 61, 62, 63, 70, 71, 72, 80, 81, 90, 100, 101, 102, 103, 104, 105, 106, 107, 108, 110, 111, 112, 113, 114 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Numbers k such that A113217(k) = A179081(k).

Complement of A298638.

Agrees with A039691 until a(65): A039691(65) = 109 is not in this sequence.

LINKS

J. Stauduhar, Table of n, a(n) for n = 1..10000

MATHEMATICA

fQ[n_] := Mod[Plus @@ IntegerDigits@n, 2] == Mod[Mod[n -1, 9] +1, 2]; fQ[0] = True; Select[ Range[0, 104], fQ] (* Robert G. Wilson v, Jan 26 2018 *)

PROG

(PYTHON)

#Digital sum of n.

def ds(n):

  if n < 10:

    return n

  return n % 10 + ds(n//10)

def A298639(term_count):

  seq = []

  m = 0

  n = 1

  while n <= term_count:

    s = ds(m)

    r = ((m - 1) % 9) + 1 if m else 0

    if s % 2 == r % 2:

      seq.append(m)

      n += 1

    m += 1

  return seq

print(A298639(100))

(PARI) dr(n)=if(n, (n-1)%9+1);

isok(n) = (sumdigits(n) % 2) == (dr(n) % 2); \\ Michel Marcus, Jan 26 2018

(PARI) is(n)=bittest(sumdigits(n)-(n-1)%9, 0)||!n \\ M. F. Hasler, Jan 26 2018

CROSSREFS

Cf. A007953, A010888, A113217, A179081, A298638, A039691.

Sequence in context: A295020 A298359 A039691 * A276347 A076121 A239427

Adjacent sequences:  A298636 A298637 A298638 * A298640 A298641 A298642

KEYWORD

nonn,easy,base

AUTHOR

J. Stauduhar, Jan 26 2018

STATUS

approved

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Last modified June 4 07:59 EDT 2020. Contains 334822 sequences. (Running on oeis4.)