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

19, 28, 29, 37, 38, 39, 46, 47, 48, 49, 55, 56, 57, 58, 59, 64, 65, 66, 67, 68, 69, 73, 74, 75, 76, 77, 78, 79, 82, 83, 84, 85, 86, 87, 88, 89, 119, 128, 129, 137, 138, 139, 146, 147, 148, 149

Offset: 1

Author

David Radcliffe, Nov 23 2010

Keywords

• nonn
• base

Comments

Note that the first 18 multiples of 11 have even digital sums.

Indices of odd entries in A136614. - R. J. Mathar, Nov 23 2010

a(n) = A075517(n+9) = A248013(n+10) for n <= 36. - Giovanni Resta, Sep 04 2017

Examples

			19 is on the list because 11*19 = 209 and 2+0+9 is odd.
		

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A008593, A007953.

Programs

Haskell

a173639 n = a173639_list !! (n-1)
a173639_list = filter (odd . a007953 . (* 11)) [0..]
-- Reinhard Zumkeller, Jul 05 2014

Maple

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;

Mathematica

Select[Range[200],OddQ[Total[IntegerDigits[11#]]]&] (* Harvey P. Dale, May 28 2012 *)

Python

ans = []
for n in range(1,151):
    N,s = 11*n,0
    while N:
        s += N % 10
        N //= 10
    if s % 2:
        ans.append(n)
print(ans)