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A239870 Noncube perfect powers. [Warning: definition does not match the DATA.] 5
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 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
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
LINKS
FORMULA
A052409(a(n)) mod 3 > 0.
PROG
(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
CROSSREFS
Cf. A097054, A239728, intersection of A007412 and A001597.
Sequence in context: A326958 A281904 A007679 * A068037 A167188 A295720
KEYWORD
nonn,obsc
AUTHOR
Reinhard Zumkeller, Mar 28 2014
STATUS
approved

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Last modified March 19 04:58 EDT 2024. Contains 370952 sequences. (Running on oeis4.)