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A025620
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Numbers of form 4^i*9^j, with i, j >= 0.
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4
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1, 4, 9, 16, 36, 64, 81, 144, 256, 324, 576, 729, 1024, 1296, 2304, 2916, 4096, 5184, 6561, 9216, 11664, 16384, 20736, 26244, 36864, 46656, 59049, 65536, 82944, 104976, 147456, 186624, 236196, 262144, 331776, 419904, 531441, 589824, 746496, 944784
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listen;
history;
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internal format)
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OFFSET
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1,2
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COMMENTS
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Numbers of form 2^(2*i)*3^(2*j)) or 3-smooth squares: intersection of A003586 and A000290; A001221(a(n)) <= 2; A001222(a(n)) is even; A006530(a(n)) <= 3. - Reinhard Zumkeller, May 16 2015
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LINKS
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Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
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PROG
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(Haskell)
import Data.Set (singleton, deleteFindMin, insert)
a025620 n = a025620_list !! (n-1)
a025620_list = f $ singleton 1 where
f s = y : f (insert (4 * y) $ insert (9 * y) s')
where (y, s') = deleteFindMin s
-- Reinhard Zumkeller, May 16 2015
(PARI) list(lim)=my(v=List(), N); for(n=0, logint(lim\=1, 9), N=9^n; while(N<=lim, listput(v, N); N<<=2)); Set(v) \\ Charles R Greathouse IV, Jan 10 2018
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CROSSREFS
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Cf. A003586, A000290, A001221, A001222, A006530, subsequence of A036667.
Sequence in context: A000548 A256944 A106575 * A117218 A226076 A272711
Adjacent sequences: A025617 A025618 A025619 * A025621 A025622 A025623
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KEYWORD
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easy,nonn
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AUTHOR
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David W. Wilson
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STATUS
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approved
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