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 A345309 Numbers whose digital sum coincides with digital sum of their largest proper divisor. 0
 18, 27, 36, 54, 72, 81, 90, 108, 126, 135, 144, 162, 180, 198, 216, 234, 243, 252, 270, 297, 306, 324, 342, 351, 360, 361, 378, 396, 405, 414, 432, 450, 504, 513, 522, 540, 551, 558, 567, 576, 594, 612, 621, 630, 702, 703, 720, 738, 756, 774, 792, 810, 837 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Many of the numbers are multiples of 9. The ones that are not form sequence A219340. LINKS EXAMPLE The largest proper divisor of 54 is 27. The sum of digits of 54 and 27 are the same. Thus 54 is in this sequence. The largest proper divisor of 63 is 21. The sum of digits of 63 and 21 are not the same. Thus 63 is not in this sequence. MATHEMATICA Select[Range[2, 10000], Total[IntegerDigits[#]] == Total[IntegerDigits[Divisors[#][[-2]]]] &] PROG (Python) from sympy import divisors def sd(n): return sum(map(int, str(n))) def ok(n): return sd(n) == sd(divisors(n)[-2]) print(list(filter(ok, range(2, 840)))) # Michael S. Branicky, Jun 13 2021 CROSSREFS Cf. A219340. Sequence in context: A109911 A239878 A065751 * A337752 A279108 A038632 Adjacent sequences:  A345306 A345307 A345308 * A345310 A345311 A345312 KEYWORD nonn,base AUTHOR Tanya Khovanova, Jun 13 2021 STATUS approved

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Last modified May 16 03:58 EDT 2022. Contains 353688 sequences. (Running on oeis4.)