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Search: id:A133219
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| A133219 |
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Smallest composite integer in base n which remains composite after altering any one or two digits. |
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+0
1
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| 1010100, 2200100, 20130000, 3243003420, 55111253530, 5411665056000, 33254100107730, 210324811482600, 977731833235239280
(list; graph; listen)
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OFFSET
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2,1
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COMMENT
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Changing the most significant digit to 0 is allowed. The problem (base 10) was posed by W. Sierpinski, published in 1977. There are an infinite number of solutions if a certain Erdos conjecture on congruences is true. a(2) through a(9) are proved minimal, a(10) has not yet been proved minimal.
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LINKS
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Witold Jarnicki and Maciej Zenczykowski, On a property of the number 977731833235239280.
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EXAMPLE
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a(3) base 10 = 1953. a(4) base 10 = 34560. a(5) base 10 = 7000485. a(6) base 10 = 354748446. a(7) base 10 = 77478704205. a(8) base 10 = 1878528135128. a(9) base 10 = 48398467146642.
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CROSSREFS
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Sequence in context: A059925 A065327 A066354 this_sequence A043643 A096931 A066598
Adjacent sequences: A133216 A133217 A133218 this_sequence A133220 A133221 A133222
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KEYWORD
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base,more,nonn
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AUTHOR
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Jonathan Vos Post (jvospost3(AT)gmail.com), Oct 11 2007
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EXTENSIONS
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a(2) and the definition were corrected by Witold Jarnicki, Oct 11 2007
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