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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
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
KEYWORD
nonn,base
AUTHOR
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.)