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Search: id:A109055
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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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+0
7
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| 1, 1, 3, 24, 541, 35649, 6979689, 4085743032, 7166723910237, 37698139930450365, 594816080266215640710, 28154472624850002001979592, 3997853576535778666975681355079, 1703042427700923785323670557504832751
(list; graph; listen)
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OFFSET
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0,3
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COMMENT
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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
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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
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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
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Cf. A107354, A109056, A109057, A109058, A109059, A109060, A109061, A109062.
Cf. A115728, A115729.
Sequence in context: A010791 A065761 A002832 this_sequence A056207 A075655 A000856
Adjacent sequences: A109052 A109053 A109054 this_sequence A109056 A109057 A109058
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KEYWORD
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nonn
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AUTHOR
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A. O. Munagi (amunagi(AT)yahoo.com), Jun 17 2005
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EXTENSIONS
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More terms from Paul D. Hanna (pauldhannaATjuno.com)
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