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A122494
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Set of numbers of the form a^b with 2<=a<=b (rare powers?), sorted.
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3
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4, 8, 16, 27, 32, 64, 81, 128, 243, 256, 512, 729, 1024, 2048, 2187, 3125, 4096, 6561, 8192, 15625, 16384, 19683, 32768, 46656, 59049, 65536, 78125, 131072, 177147, 262144, 279936, 390625, 524288, 531441, 823543, 1048576, 1594323, 1679616
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OFFSET
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1,1
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LINKS
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EXAMPLE
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279936 is there because it is 6^7.
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PROG
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(Haskell)
import Data.Set (singleton, deleteFindMin, insert)
a122494 n = a122494_list !! (n-1)
a122494_list = f (singleton (4, 2)) 27 [3..] where
f s uu us@(u:us'@(u':_))
| vv > uu = uu : f (insert (uu * u, u) s) (u' ^ u') us'
| vv < uu = vv : f (insert (vv * v, v) s') uu us
| otherwise = vv : f (insert (vv * v, v) s') (u' ^ u') us'
where ((vv, v), s') = deleteFindMin s
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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Paul Stoeber (pstoeber(AT)uni-potsdam.de), Sep 16 2006
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STATUS
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approved
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