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Search: id:A080674
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| 0, 4, 20, 84, 340, 1364, 5460, 21844, 87380, 349524, 1398100, 5592404, 22369620, 89478484, 357913940, 1431655764, 5726623060, 22906492244, 91625968980, 366503875924, 1466015503700, 5864062014804, 23456248059220, 93824992236884, 375299968947540, 1501199875790164
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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a(n) is the number of steps which are made when generating all n-step random walks that begin in a given point P on a two-dimensional square lattice. To make one step means to move along one edge on the lattice. - Pawel P. Mazur (Pawel.Mazur(AT)pwr.wroc.pl), Mar 10 2005
Conjectured to be the number of integers from 0 to (10^n)-1 that lack 0, 1, 2, 3, 4 and 5 as a digit . - Alexandre Wajnberg (alexandre.wajnberg(AT)ulb.ac.be), Apr 25 2005
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FORMULA
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a(n) = Sum_{i = 1 to n} 4^i. - Adam McDougall (mcdougal(AT)stolaf.edu), Sep 29 2004
a(n) = 4a(n-1) + 4 - Alexandre Wajnberg (alexandre.wajnberg(AT)ulb.ac.be), Apr 25 2005
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MAPLE
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a:=n->sum (4^j, j=1..n): seq(a(n), n=0..24); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Oct 03 2007
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CROSSREFS
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a(n) = 2 * A020988(n) = A002450(n+1)-1 = 4 * A002450(n).
Sequence in context: A099898 A003489 A084240 this_sequence A110154 A093357 A027156
Adjacent sequences: A080671 A080672 A080673 this_sequence A080675 A080676 A080677
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KEYWORD
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nonn
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AUTHOR
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njas, Mar 02 2003
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