login

Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.

Numbers k whose base-10 representation Sum_{i=0..m} d(i)*10^(m-i) has d(i)=0 for all odd i. Here m is the position of the lead digit of k.
4

%I #27 Apr 12 2022 22:29:23

%S 0,1,2,3,4,5,6,7,8,9,10,20,30,40,50,60,70,80,90,100,101,102,103,104,

%T 105,106,107,108,109,200,201,202,203,204,205,206,207,208,209,300,301,

%U 302,303,304,305,306,307,308,309,400,401,402,403

%N Numbers k whose base-10 representation Sum_{i=0..m} d(i)*10^(m-i) has d(i)=0 for all odd i. Here m is the position of the lead digit of k.

%C Every nonnegative integer can be represented as the sum of two members of this sequence. - _Franklin T. Adams-Watters_, Aug 30 2014

%C This first differs from A236402 at a(110)=1000 (followed by 1010, 1020, 1030, ...), while A236402(110)=910 (followed by 1000, 1001, 1002, ...). - _M. F. Hasler_, Dec 28 2014

%H Robert Israel, <a href="/A032945/b032945.txt">Table of n, a(n) for n = 1..10000</a>

%p N:= 6: # to get all terms with up to N digits

%p A[1]:= 0:

%p count:= 1:

%p for d from 1 to N do

%p dp:= ceil(d/2);

%p for j from 10^(dp-1) to 10^dp-1 do

%p L:= ListTools[Reverse](convert(j,base,10));

%p L:= ListTools[Interleave](L,[0$(d-dp)]);

%p count:= count+1;

%p A[count]:= add(L[i]*10^(d-i),i=1..d);

%p od

%p od:

%p seq(A[i],i=1..count); # _Robert Israel_, Aug 31 2014

%o (PARI) is(n)=!forstep(i=2,#n=digits(n),2,n[i]&&return) \\ _M. F. Hasler_, Dec 28 2014

%o (Python)

%o def ok(n): return str(n)[1::2].strip('0') == ""

%o print([k for k in range(404) if ok(k)]) # _Michael S. Branicky_, Apr 12 2022

%Y Cf. A126684.

%K nonn,base

%O 1,3

%A _Clark Kimberling_

%E Definition corrected by _Franklin T. Adams-Watters_, Aug 30 2014