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A109055
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To compute a(n) we first write down 3^n 1's in a row. Each row takes the rightmost 3rd part of the previous row and each element in it equals sum of the elements of the previous row starting with the first of the rightmost 3rd part. The single element in the last row is a(n).
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6
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1, 1, 3, 24, 541, 35649, 6979689, 4085743032, 7166723910237, 37698139930450365, 594816080266215640710, 28154472624850002001979592, 3997853576535778666975681355079, 1703042427700923785323670557504832751
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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COMMENTS
| Comment from Frank Adams-Watters (FrankTAW(AT)Netscape.net), Jul 13 2006: This is the number of subpartitions of the sequence 3^n-1. As such it can also be computed adding forward, with 3^n terms in the n-th line:
1...........................................................................
1.1 1.......................................................................
1.2.3.3..3..3..3..3..3......................................................
1.3.6.9.12.15.18.21.24.24.24.24.24.24.24.24.24.24.24.24.24.24.24.24.24.24.24
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EXAMPLE
| For example, for n=3 the array looks like this:
1..1..1..1..1........1..1..1..1..1..1..1..1..1..1
........................1..2..3..4..5..6..7..8..9
..........................................7.15.24
...............................................24
Therefore a(3)=24.
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MAPLE
| proc(n::nonnegint) local f, a; if n=0 or n=1 then return 1; end if; f:=L->[seq(add(L[i], i=2*nops(L)/3+1..j), j=2*nops(L)/3+1..nops(L))]; a:=f([seq(1, j=1..3^n)]); while nops(a)>3 do a:=f(a) end do; a[3]; end proc;
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CROSSREFS
| Cf. A107354, A109056, A109057, A109058, A109059, A109060, A109061, A109062.
Cf. A115728, A115729.
Sequence in context: A185970 A194157 A166736 * A202944 A056207 A075655
Adjacent sequences: A109052 A109053 A109054 * A109056 A109057 A109058
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KEYWORD
| nonn
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AUTHOR
| A. O. Munagi (amunagi(AT)yahoo.com), Jun 17 2005
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EXTENSIONS
| More terms from Paul D. Hanna (pauldhannaATjuno.com)
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