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A122494 Set of numbers of the form a^b with 2<=a<=b (rare powers?), sorted. 3
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

EXAMPLE

279936 is there because it is 6^7.

PROG

(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

-- Reinhard Zumkeller, May 01 2015

CROSSREFS

Subsequences: A000312, A257278.

Sequence in context: A068936 A054744 A100391 * A257278 A257279 A299894

Adjacent sequences:  A122491 A122492 A122493 * A122495 A122496 A122497

KEYWORD

nonn

AUTHOR

Paul Stoeber (pstoeber(AT)uni-potsdam.de), Sep 16 2006

STATUS

approved

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Last modified February 18 05:30 EST 2019. Contains 320245 sequences. (Running on oeis4.)