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A351478
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Numbers whose sum of even digits is twice the sum of odd digits.
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1
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12, 21, 36, 63, 102, 114, 120, 138, 141, 183, 201, 210, 234, 243, 258, 285, 306, 318, 324, 342, 360, 381, 411, 423, 432, 456, 465, 528, 546, 564, 582, 603, 630, 645, 654, 678, 687, 768, 786, 813, 825, 831, 852, 867, 876, 1002, 1014, 1020, 1038, 1041, 1083, 1104, 1116, 1122, 1140, 1161, 1200, 1212
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OFFSET
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1,1
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COMMENTS
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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
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LINKS
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EXAMPLE
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a(1) = 12 whose sum of even digits (4) is twice the sum of odd digits (2);
a(2) = 21 whose sum of even digits (4) is twice the sum of odd digits (2);
a(3) = 36 whose sum of even digits (6) is twice the sum of odd digits (3);
etc.
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MATHEMATICA
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Select[Range[1000], Plus @@ Select[IntegerDigits[#], EvenQ] == 2 * Plus @@ Select[IntegerDigits[#], OddQ] &] (* Amiram Eldar, Feb 12 2022 *)
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PROG
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(Python)
def ok(n):
ds = list(map(int, str(n)))
return sum(d for d in ds if d%2==0) == 2*sum(d for d in ds if d%2==1)
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CROSSREFS
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KEYWORD
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base,nonn
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AUTHOR
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STATUS
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approved
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