A197181 Numbers that are a divisor of the product of the factorials of their digits in decimal representation.
1, 2, 3, 4, 5, 6, 7, 8, 9, 15, 16, 18, 24, 28, 36, 45, 48, 60, 64, 70, 72, 75, 80, 84, 90, 96, 98, 128, 144, 168, 175, 180, 189, 192, 256, 280, 288, 360, 378, 384, 448, 480, 486, 567, 576, 588, 640, 648, 672, 675, 720, 729, 756, 768, 784, 840, 864, 875, 882
Offset: 1
Examples
a(10)=15: A066459(15) = 1!*5! = 120 = 15 * 8; a(11)=16: A066459(16) = 1!*6! = 720 = 16 * 45; 17 is not a term because 5040 mod 17 = 8, A066459(16) = 5040; a(12)=18: A066459(15) = 1!*8! = 40320 = 18 * 2240.
Links
- Reinhard Zumkeller, Table of n, a(n) for n = 1..1000
Programs
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Haskell
import Data.List (elemIndices) a197181 n = a197181_list !! (n-1) a197181_list = map (+ 1) $ elemIndices 0 $ zipWith mod (map a066459 [1..]) [1..]
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Mathematica
Select[Range[900],IntegerQ[Times@@(IntegerDigits[#]!)/#]&] (* Harvey P. Dale, Jul 07 2019 *)