cp's OEIS Frontend

A298638 Numbers k such that the digital sum of k and the digital root of k have opposite parity.

%I A298638 #35 Sep 25 2023 14:51:40
%S A298638 19,28,29,37,38,39,46,47,48,49,55,56,57,58,59,64,65,66,67,68,69,73,74,
%T A298638 75,76,77,78,79,82,83,84,85,86,87,88,89,91,92,93,94,95,96,97,98,99,
%U A298638 109,118,119,127,128,129,136,137,138,139,145,146,147,148,149,154,155
%N A298638 Numbers k such that the digital sum of k and the digital root of k have opposite parity.
%C A298638 Numbers k such that A113217(k) <> A179081(k).
%C A298638 Complement of A298639.
%C A298638 Agrees with A291884 until a(46): a(46) = 109 is not in that sequence.
%H A298638 J. Stauduhar, <a href="/A298638/b298638.txt">Table of n, a(n) for n = 1..10000</a>
%t A298638 Select[Range[145], EvenQ@ Total@ IntegerDigits@ # != EvenQ@ NestWhile[Total@ IntegerDigits@ # &, #, # > 9 &] &] (* _Michael De Vlieger_, Feb 03 2018 *)
%o A298638 (Python)
%o A298638 #Digital sum of n.
%o A298638 def ds(n):
%o A298638   if n < 10:
%o A298638     return n
%o A298638   return n % 10 + ds(n//10)
%o A298638 def A298638(term_count):
%o A298638   seq = []
%o A298638   m = 0
%o A298638   n = 1
%o A298638   while n <= term_count:
%o A298638     s = ds(m)
%o A298638     r = ((m - 1) % 9) + 1 if m else 0
%o A298638     if s % 2 != r % 2:
%o A298638       seq.append(m)
%o A298638       n += 1
%o A298638     m += 1
%o A298638   return seq
%o A298638 print(A298638(100))
%o A298638 (PARI) isok(n) = sumdigits(n) % 2 != if (n, ((n-1)%9+1) % 2, 0); \\ _Michel Marcus_, Mar 01 2018
%Y A298638 Cf. A007953, A010888, A113217, A179081.
%Y A298638 Cf. A298639, A291884.
%K A298638 nonn,easy,base
%O A298638 1,1
%A A298638 _J. Stauduhar_, Jan 23 2018