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1, 2, 6, 16, 38, 84, 178, 368, 750, 1516, 3050, 6120, 12262, 24548, 49122, 98272, 196574, 393180, 786394, 1572824, 3145686, 6291412, 12582866, 25165776, 50331598, 100663244, 201326538, 402653128, 805306310, 1610612676, 3221225410, 6442450880, 12884901822, 25769803708
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| Contribution from Johannes W. Meijer (meijgia(AT)hotmail.com), Aug 15 2010: (Start)
An elephant sequence, see A175654. For the corner squares four A[5] vectors, with decimal values 58, 154, 178 and 184, lead to this sequence. For the central square these vectors lead to the companion sequence A033484.
(End)
a(n) is also the number of order-preserving partial isometries of an n-chain, i.e., the row sums of A183153 and A183154. - Abdullahi Umar, Dec 28 2010
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LINKS
| Harvey P. Dale, Table of n, a(n) for n = 0..1000
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FORMULA
| G.f. : (1-2x+3x^2)/((1-x)^2(1-2x)); a(n)=2a(n-1)+2n-2, n>0, a(0)=1; a(n)=4a(n-1)-5a(n-2)+2a(n-3).
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MATHEMATICA
| s=2; lst={1, s}; Do[s+=(s+=n); AppendTo[lst, s], {n, 5!}]; lst [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Oct 11 2008]
Table[3 2^n-2n-2, {n, 0, 40}] (* or *) LinearRecurrence[{4, -5, 2}, {1, 2, 6}, 40] (* From Harvey P. Dale, Oct 25 2011 *)
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CROSSREFS
| Cf. A079583.
Sequence in context: A128232 A099099 A074082 * A167821 A093041 A156616
Adjacent sequences: A097810 A097811 A097812 * A097814 A097815 A097816
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KEYWORD
| easy,nonn
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AUTHOR
| Paul Barry (pbarry(AT)wit.ie), Aug 25 2004
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EXTENSIONS
| Alternative description, additional reference and crossrefs
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