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Search: id:A113918
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| A113918 |
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Cardinality of Image^inf({ 2 }) under repeated base-n zero-split squaring. |
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2
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OFFSET
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2,1
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COMMENT
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Define f_b(x) to be the set of base b numbers left after splitting x^2 at its zero digits, and Image_b(S) = union_{x in S}{ { x } union f_b(S) }, then a(n) = | Image_n^inf({ 2 }) |
Conjecture: a(n) is finite for all n
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EXAMPLE
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f_10(29648) = { 4, 39, 879 } since 29648^2 = 879003904
a(8) = 2 since Image_8({ 2 }) = { 2, 4 } and f_8({ 2, 4 }) = { 2, 4 }, and |{ 2, 4 }| is 2.
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CROSSREFS
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Cf. A113917.
Sequence in context: A003819 A112969 A077452 this_sequence A094048 A087665 A093481
Adjacent sequences: A113915 A113916 A113917 this_sequence A113919 A113920 A113921
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KEYWORD
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nonn,hard
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AUTHOR
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Hugo van der Sanden (hv(AT)crypt.org) extending a suggestion from David W. Wilson End., Jan 31 2006
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