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A113918 Cardinality of Image^inf({ 2 }) under repeated base-n zero-split squaring. 2
2, 18, 2, 3050, 34762, 3087549, 2 (list; graph; refs; listen; history; text; internal format)
OFFSET
2,1
COMMENTS
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.
LINKS
Hugo van der Sanden, Perl and C implementations, Feb 03 2015
EXAMPLE
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.
CROSSREFS
Cf. A113917.
Sequence in context: A266166 A077452 A353309 * A253603 A094048 A179073
KEYWORD
nonn,hard
AUTHOR
Hugo van der Sanden extending a suggestion from David W. Wilson, Jan 31 2006
EXTENSIONS
Corrected by Hugo van der Sanden, Feb 03 2015
STATUS
approved

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Last modified April 18 11:52 EDT 2024. Contains 371779 sequences. (Running on oeis4.)