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A006895
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Parenthesized one way gives the powers of 2: (1), (2), (1+3), ..., another way the powers of 3: (1), (2+1), (3+6), ....
(Formerly M0158)
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3
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1, 2, 1, 3, 6, 2, 16, 9, 23, 58, 6, 128, 109, 147, 512, 70, 954, 1233, 815, 4096, 1650, 6542, 13141, 3243, 32768, 23038, 42498, 131072, 3577, 258567, 272874, 251414, 1048576, 294333, 1802819, 2980150, 1214154, 8388608, 4746145, 12031071, 31015650, 2538782
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OFFSET
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0,2
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COMMENTS
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Powers of 2 need 1 term or 2 terms parenthesized, whereas powers of 3 need 2 or 3 terms parenthesized, when 3 then the middle term is a power of 2. See A227928. - Reinhard Zumkeller, Oct 09 2013
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REFERENCES
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N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
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EXAMPLE
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. a(0) = _^0
. a(1) = 2^1
. a(1) + a(2) = 2 + 1 = 3^1
. a(2) + a(3) = 1 + 3 = 4 = 2^2
. a(3) + a(4) = 3 + 6 = 9 = 3^2
. a(4) + a(5) = 6 + 2 = 8 = 2^3
. a(6) = 16 = 2^4
. a(5) + a(6) + a(7) = 2 + 16 + 9 = 27 = 3^3
. a(7) + a(8) = 9 + 23 = 32 = 2^5
. a(8) + a(9) = 23 + 58 = 81 = 3^4
. a(9) + a(10) = 58 + 6 = 64 = 2^6
. a(11) = 128 = 2^7
. a(10) + a(11) + a(12) = 6 + 128 + 109 = 243 = 3^5
. a(12) + a(13) = 109 + 147 = 256 = 2^8
. a(14) = 512 = 2^9
. a(13) + a(14) + a(15) = 147 + 512 + 70 = 3^6 = 729 .
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PROG
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(Haskell)
a006895 n = a006895_list !! n
a006895_list = 1 : f 0 0 (tail a000079_list) (tail a000244_list) where
f x y us'@(u:us) vs'@(v:vs)
| x > 0 = (u - x) : f 0 (u - x + y) us vs'
| y > v - u = (v - y) : f (v + x - y) 0 us' vs
| otherwise = u : f 0 (u + y) us vs'
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CROSSREFS
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KEYWORD
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nonn,nice
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AUTHOR
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STATUS
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approved
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