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%I #9 Jan 29 2014 04:03:55
%S 0,-1,-2,-3,-4,-5,-6,-7,-8,-9,0,1,2,3,4,5,6,7,8,9,0,2,4,6,8,10,12,14,
%T 16,18,0,3,6,9,12,15,18,21,24,27,0,4,8,12,16,20,24,28,32,36,0,5,10,15,
%U 20,25,30,35,40,45,0,6,12,18,24,30,36,42,48,54,0,7,14,21,28,35,42,49,56,63,0,8,16,24,32,40,48,56,64
%N Product of negated digits of n.
%C a(n) = A007954(n) * (-1)^A055642(n).
%H Reinhard Zumkeller, <a href="/A187844/b187844.txt">Table of n, a(n) for n = 0..25000</a>
%e a(289) = (-2) * (-8) * (-9) = -144;
%e a(2891) = (-2) * (-8) * (-9) * (-1) = 144.
%o (Haskell)
%o import Data.Char (digitToInt)
%o a187844 n = product $ map (negate . fromIntegral . digitToInt) $ show n
%Y Cf. A187845 (partial sums).
%K sign,base,look
%O 0,3
%A _Reinhard Zumkeller_, Mar 14 2011
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