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 A172509 Numbers n such that Omega(n) = Omega(n - (digital sum of n)). 1
 1, 10, 14, 15, 20, 27, 28, 30, 40, 50, 52, 60, 70, 75, 76, 78, 80, 90, 102, 105, 112, 124, 125, 132, 135, 136, 140, 164, 165, 176, 182, 186, 188, 204, 212, 224, 232, 234, 248, 252, 264, 273, 275, 279, 280, 290, 292, 306, 308, 315, 328, 336, 343 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Omega(n) is the number of prime divisors of n, A001222 (for n>0), taking Omega(0)=0. Omega(a(n)) >= 3 for n >= 5. - Robert Israel, Jul 04 2019 LINKS Robert Israel, Table of n, a(n) for n = 1..10000 EXAMPLE a(1)=1 because Omega(1) = Omega(1 - (digital sum of 1)) = Omega(0) = 0; a(2)=10 because Omega(10) = Omega(10 - (digital sum of 10)) = Omega(9) = 2. MAPLE filter:= proc(n) uses numtheory: bigomega(n) = bigomega(n - convert(convert(n, base, 10), `+`)) end proc: select(filter, [\$1..500]); # Robert Israel, Jul 04 2019 MATHEMATICA Join[{1}, Select[Range[2, 400], PrimeOmega[#]==PrimeOmega[#-Total[ IntegerDigits[ #]]]&]] (* Harvey P. Dale, Jun 21 2021 *) CROSSREFS Cf. A001222. Sequence in context: A209800 A119613 A154371 * A036338 A108793 A100929 Adjacent sequences: A172506 A172507 A172508 * A172510 A172511 A172512 KEYWORD nonn,base AUTHOR Juri-Stepan Gerasimov, Nov 21 2010 EXTENSIONS Corrected and edited by D. S. McNeil, Nov 21 2010 STATUS approved

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Last modified March 1 04:59 EST 2024. Contains 370430 sequences. (Running on oeis4.)