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A121759
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In decimal number system, take even digits of n with negative sign.
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3
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1, -2, 3, -4, 5, -6, 7, -8, 9, 10, 11, 8, 13, 6, 15, 4, 17, 2, 19, -20, -19, -22, -17, -24, -15, -26, -13, -28, -11, 30, 31, 28, 33, 26, 35, 24, 37, 22, 39, -40, -39, -42, -37, -44, -35, -46, -33, -48, -31, 50, 51, 48, 53, 46, 55, 44, 57, 42, 59, -60, -59, -62, -57, -64, -55, -66, -53, -68, -51, 70, 71, 68, 73, 66, 75, 64, 77, 62
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| See A121758. In decimal number system, take odd digits of n with negative sign.
a(A014261(n)) = A014261(n). - Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Nov 30 2007
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LINKS
| Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
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FORMULA
| If n = d(i)*10^(i-1), then a(n) = (-1)^(1+d(i))*d(i)*10^(i-1).
a(n) = -A121758(n).
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EXAMPLE
| a(12) = 8 because 12 = 1*10^1 + 2*10^0 and a(12) = (-1)^(1+1)*1*10^1 + (-1)^(1+2)*2*10^0 = 10-2 = 8.
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PROG
| (Haskell)
import Data.List (unfoldr)
a121759 = foldl f 0 . reverse . unfoldr d where
d 0 = Nothing
d x = Just $ swap $ divMod x 10
f v d | even d = 10 * v - d
| odd d = 10 * v + d
-- Reinhard Zumkeller, Aug 01 2011
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CROSSREFS
| Cf. A121758.
Sequence in context: A043271 A062759 A121758 * A180613 A072778 A178787
Adjacent sequences: A121756 A121757 A121758 * A121760 A121761 A121762
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KEYWORD
| base,sign,nice
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AUTHOR
| Zak Seidov (zakseidov(AT)yahoo.com), Aug 20 2006
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