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A034797
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a(0) = 0; a(n+1) = a(n) + 2^a(n).
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18
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OFFSET
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0,3
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COMMENTS
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First impartial game with value n, using natural enumeration of impartial games.
The natural 1-1 correspondence between nonnegative numbers and hereditarily finite sets is given by f(A)=sum over members m of A of 2^f(m). A set can be considered an impartial game where the legal moves are the members. The value of an impartial game is always an ordinal (for finite games, an integer).
The next term, a(5) = 2^2059 + 2059, has 620 decimal digits and is too large to include. - Olivier Gérard, Jun 26 2001
The first n terms in this sequence form the lexicographically earliest n-vertex clique in the Ackermann-Rado encoding of the Rado graph (an infinite graph in which vertex i is adjacent to vertex j, with i<j, when the i-th bit of the binary representation of j is nonzero). - David Eppstein, Aug 22 2014
This sequence was used by Spiro to bound the density of refactorable numbers (A033950). - David Eppstein, Aug 22 2014
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REFERENCES
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J. H. Conway, On Numbers and Games, Academic Press.
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LINKS
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MATHEMATICA
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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Joseph Shipman (shipman(AT)savera.com)
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STATUS
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approved
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