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Numbers whose sum of even digits is twice the sum of odd digits.
1

%I #14 Feb 12 2022 13:43:03

%S 12,21,36,63,102,114,120,138,141,183,201,210,234,243,258,285,306,318,

%T 324,342,360,381,411,423,432,456,465,528,546,564,582,603,630,645,654,

%U 678,687,768,786,813,825,831,852,867,876,1002,1014,1020,1038,1041,1083,1104,1116,1122,1140,1161,1200,1212

%N Numbers whose sum of even digits is twice the sum of odd digits.

%C The sequence is closed under concatenation (if k and m are terms, so are k.m and m.k); permutation of a term's string of digits; and insertion of 0's within a term's string of digits. - _Michael S. Branicky_, Feb 12 2022

%e a(1) = 12 whose sum of even digits (4) is twice the sum of odd digits (2);

%e a(2) = 21 whose sum of even digits (4) is twice the sum of odd digits (2);

%e a(3) = 36 whose sum of even digits (6) is twice the sum of odd digits (3);

%e etc.

%t Select[Range[1000], Plus @@ Select[IntegerDigits[#], EvenQ] == 2 * Plus @@ Select[IntegerDigits[#], OddQ] &] (* _Amiram Eldar_, Feb 12 2022 *)

%o (Python)

%o def ok(n):

%o ds = list(map(int, str(n)))

%o return sum(d for d in ds if d%2==0) == 2*sum(d for d in ds if d%2==1)

%o print([k for k in range(1, 2173) if ok(k)]) # _Michael S. Branicky_, Feb 12 2022

%Y Cf. A036301, A351479.

%K base,nonn

%O 1,1

%A _Eric Angelini_ and _Carole Dubois_, Feb 12 2022