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

1,1

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

Links

Table of n, a(n) for n=1..57.

Example

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).

Mathematica

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

Prog

(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

Crossrefs

Cf. A036301, A351478.

Sequence in context: A341992 A077378 A031509 * A247616 A119426 A138059

Adjacent sequences: A351476 A351477 A351478 * A351480 A351481 A351482

Keyword

base,nonn

Author

Carole Dubois and Eric Angelini, Feb 12 2022

Status

approved