cp's OEIS Frontend

A173639 Numbers n such that the sum of the digits of 11*n is odd.

%I A173639 #24 May 09 2021 08:16:34
%S A173639 19,28,29,37,38,39,46,47,48,49,55,56,57,58,59,64,65,66,67,68,69,73,74,
%T A173639 75,76,77,78,79,82,83,84,85,86,87,88,89,119,128,129,137,138,139,146,
%U A173639 147,148,149
%N A173639 Numbers n such that the sum of the digits of 11*n is odd.
%C A173639 Note that the first 18 multiples of 11 have even digital sums.
%C A173639 Indices of odd entries in A136614. - _R. J. Mathar_, Nov 23 2010
%C A173639 a(n) = A075517(n+9) = A248013(n+10) for n <= 36. - _Giovanni Resta_, Sep 04 2017
%H A173639 Harvey P. Dale, <a href="/A173639/b173639.txt">Table of n, a(n) for n = 1..1000</a>
%e A173639 19 is on the list because 11*19 = 209 and 2+0+9 is odd.
%p A173639 L := []; for n to 150 do if `mod`(add(i, i = convert(11*n, base, 10)), 2) = 1 then L := [op(L), n] end if end do; L;
%t A173639 Select[Range[200],OddQ[Total[IntegerDigits[11#]]]&] (* _Harvey P. Dale_, May 28 2012 *)
%o A173639 (Python)
%o A173639 ans = []
%o A173639 for n in range(1,151):
%o A173639     N,s = 11*n,0
%o A173639     while N:
%o A173639         s += N % 10
%o A173639         N //= 10
%o A173639     if s % 2:
%o A173639         ans.append(n)
%o A173639 print(ans)
%o A173639 (Haskell)
%o A173639 a173639 n = a173639_list !! (n-1)
%o A173639 a173639_list = filter (odd . a007953 . (* 11)) [0..]
%o A173639 -- _Reinhard Zumkeller_, Jul 05 2014
%Y A173639 Cf. A008593, A007953.
%K A173639 nonn,base
%O A173639 1,1
%A A173639 _David Radcliffe_, Nov 23 2010