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A239870
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Noncube perfect powers. [Warning: definition does not match the DATA.]
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5
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4, 9, 16, 32, 36, 49, 81, 121, 128, 144, 169, 196, 243, 256, 324, 400, 441, 484, 576, 625, 841, 900, 961, 1024, 1156, 1225, 1296, 1369, 1444, 1521, 1600, 1681, 1849, 1936, 2025, 2048, 2187, 2209, 2304, 2401, 2601, 2704, 2916, 3025, 3125, 3249, 3364, 3600
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OFFSET
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1,1
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COMMENTS
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The NAME suggests that this is an erroneous version of A340585 (which includes 25, for example), but the Haskell implementation indicates that the true definition is more complicated. - R. J. Mathar, Jan 13 2021
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LINKS
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FORMULA
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PROG
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(Haskell)
import Data.Map (singleton, findMin, deleteMin, insert)
a239870 n = a239870_list !! (n-1)
a239870_list = f 9 (3, 2) (singleton 4 (2, 2)) where
f zz (bz, ez) m
| xx < zz = if ex `mod` 3 > 0
then xx : f zz (bz, ez+1) (insert (bx*xx) (bx, ex+1) $ deleteMin m)
else f zz (bz, ez+1) (insert (bx*xx) (bx, ex+1) $ deleteMin m)
| xx > zz = if ez `mod` 3 > 0
then zz : f (zz+2*bz+1) (bz+1, 2) (insert (bz*zz) (bz, 3) m)
else f (zz+2*bz+1) (bz+1, 2) (insert (bz*zz) (bz, 3) m)
| otherwise = f (zz+2*bz+1) (bz+1, 2) m
where (xx, (bx, ex)) = findMin m -- bx ^ ex == xx
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CROSSREFS
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KEYWORD
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nonn,obsc
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AUTHOR
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STATUS
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approved
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