A227928 Powers of 2 or of 3 in order as occurring in the two ways of parenthesizing the terms in A006895.

1, 2, 3, 4, 9, 8, 16, 27, 32, 81, 64, 128, 243, 256, 512, 729, 1024, 2187, 2048, 4096, 6561, 8192, 19683, 16384, 32768, 59049, 65536, 131072, 177147, 262144, 531441, 524288, 1048576, 1594323, 2097152, 4782969, 4194304, 8388608, 14348907, 16777216, 43046721

Offset

1,2

Comments

Permutation of A006899, a(n) = A006899(n+k) for some k in {-1,0,1}.

Links

Reinhard Zumkeller, Table of n, a(n) for n = 1..1000

Example

.  n  |  a(n)                       let x denote A006895
. ----+------
.   1 |    1                     =  x(0)
.   2 |    2                     =  x(1)
.   3 |    3  =   2 +   1        =  x(1) + x(2)
.   4 |    4  =   1 +   3        =  x(2) + x(3)
.   5 |    9  =   3 +   6        =  x(3) + x(4)
.   6 |    8  =   6 +   2        =  x(4) + x(5)
.   7 |   16                     =  x(6)
.   8 |   27  =   2 +  16 +   9  =  x(5) + x(6) + x(7)
.   9 |   32  =   9 +  23        =  x(7) + x(8)
.  10 |   81  =  23 +  58        =  x(8) + x(9)
.  11 |   64  =  58 +   6        =  x(9) + x(10)
.  12 |  128                     =  x(11)
.  13 |  243  =   6 + 128 + 109  =  x(10) + x(11) + x(12)
.  14 |  256  = 109 + 147        =  x(12) + x(13)
.  15 |  512                     =  x(14)
.  16 |  729  = 147 + 512 +  70  =  x(13) + x(14) + x(15) .

Prog

(Haskell)
a227928 n = a227928_list !! (n-1)
a227928_list = 1 : f 0 0 (tail a000079_list) (tail a000244_list) where
   f x y us'@(u:us) vs'@(v:vs)
     | x > 0     = u : f 0 (u - x + y) us vs'
     | y > v - u = v : f (v + x - y) 0 us' vs
     | otherwise = u : f 0 (u + y) us vs'

Crossrefs

Sequence in context: A329449 A365117 A374445 * A098293 A095260 A171572

Adjacent sequences: A227925 A227926 A227927 * A227929 A227930 A227931

Keyword

nonn

Author

Reinhard Zumkeller, Oct 09 2013

Status

approved