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Search: id:A094812
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| A094812 |
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Number of odd composites between 2^n and 2^(n + 1). |
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+0
1
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| 0, 0, 0, 2, 3, 9, 19, 41, 85, 181, 375, 769, 1584, 3224, 6580, 13354, 27059, 54521, 110682, 223509, 450702, 908240, 1828936, 3680596, 7402790, 14883096, 29908688, 60081574, 120655821, 242228178, 486173375, 975559168, 1957148063, 3925643991
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OFFSET
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0,4
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COMMENT
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This sequence may be related to n-ary rooted trees of a fixed height. For instance, the first few terms of A036616 are:
1, 1, 1, 2, 4, 9, 19, 41, 86, 182, 376, 776, 1579, ...
and in A036622:
1, 1, 1, 2, 4, 9, 19, 42, 88, 188, 393, 821, 1692, ...
whereas in the present sequence we have:
0, 0, 0, 2, 3, 9, 19, 41, 85, 181, 375, 769, 1584, ...
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FORMULA
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Members of A071904 which lie between 2^n and 2^(n + 1)
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EXAMPLE
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2^3..2^4 = [8..16] Within this interval, the integers 9 and 15 are odd composites (9 = 3 * 3, 15 = 3 * 5).
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MATHEMATICA
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f[n_] := (2^(n - 1) - PrimePi[2^(n + 1)] + PrimePi[2^n]); Table[ f[n], {n, 32}] (from Robert G. Wilson v Jun 15 2004)
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CROSSREFS
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Cf. A036616, A036622, A071904.
Adjacent sequences: A094809 A094810 A094811 this_sequence A094813 A094814 A094815
Sequence in context: A113201 A089753 A094679 this_sequence A079992 A106519 A006866
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KEYWORD
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easy,nonn
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AUTHOR
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Andrew Plewe (aplewe(AT)sbcglobal.net), Jun 11 2004
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EXTENSIONS
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More terms from Robert G. Wilson v (rgwv(AT)rgwv.com), Jun 15 2004
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