A351479 Numbers whose sum of odd digits is twice the sum of even digits.

123, 132, 147, 174, 213, 231, 312, 321, 345, 354, 369, 396, 417, 435, 453, 471, 534, 543, 567, 576, 639, 657, 675, 693, 714, 741, 756, 765, 789, 798, 879, 897, 936, 963, 978, 987, 1023, 1032, 1047, 1074, 1203, 1227, 1230, 1272, 1302, 1320, 1407, 1470, 1704, 1722, 1740, 2013, 2031, 2103, 2127, 2130, 2172

Offset: 1

Author

Carole Dubois and Eric Angelini, Feb 12 2022

Keywords

• base
• nonn

Comments

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

Examples

			a(1) = 123 whose sum of odd digits (4) is twice the sum of even digits (2);
a(2) = 132 whose sum of odd digits (4) is twice the sum of even digits (2);
a(3) = 147 whose sum of odd digits (8) is twice the sum of even digits (4).
		

Crossrefs

Cf. A036301, A351478.

Programs

Mathematica

Select[Range[2000], Plus @@ Select[IntegerDigits[#], OddQ] == 2 * Plus @@ Select[IntegerDigits[#], EvenQ] &] (* Amiram Eldar, Feb 12 2022 *)

Python

def ok(n):
    ds = list(map(int, str(n)))
    return sum(d for d in ds if d%2==1) == 2*sum(d for d in ds if d%2==0)
print([k for k in range(1, 2173) if ok(k)]) # Michael S. Branicky, Feb 12 2022