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Search: id:A068695
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| A068695 |
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Smallest number (not beginning with 0) that yields a prime when placed on the right of n. |
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+0
4
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| 1, 3, 1, 1, 3, 1, 1, 3, 7, 1, 3, 7, 1, 9, 1, 3, 3, 1, 1, 11, 1, 3, 3, 1, 1, 3, 1, 1, 3, 7, 1, 17, 1, 7, 3, 7, 3, 3, 7, 1, 9, 1, 1, 3, 7, 1, 9, 7, 1, 3, 13, 1, 23, 1, 7, 3, 1, 7, 3, 1, 3, 11, 1, 1, 3, 1, 3, 3, 1, 1, 9, 7, 3, 3, 1, 1, 3, 7, 7, 9, 1, 1, 9, 19, 3, 3, 7, 1, 23, 7, 1, 9, 7, 1, 3, 7, 1, 3, 1, 9, 3, 1
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Many numbers become prime by appending a one-digit odd number. Some numbers (such as 20, 32, 51, etc.) require a 2-digit odd number (A032352 has these). In the first 100,000 values of n there are only 22 that require a 3-digit odd number (A091089). There probably are some values that require odd numbers of 4 or more digits, but these are likely to be very large. - Chuck Seggelin (barkeep(AT)plastereddragon.com), Dec 18 2003
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LINKS
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David W. Wilson, Table of n, a(n) for n=1..10000
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EXAMPLE
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a(20)=11 because 11 is the minimum odd number which when appended to 20 forms a prime (201, 203, 205, 207, 209 are all nonprime, 2011 is prime).
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CROSSREFS
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Cf. A032352 (a(n) requires at least a 2 digit odd number), A091089 (a(n) requires at least a 3 digit odd number).
Sequence in context: A060266 A073310 A046929 this_sequence A110787 A139002 A139378
Adjacent sequences: A068692 A068693 A068694 this_sequence A068696 A068697 A068698
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KEYWORD
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base,easy,nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Mar 03 2002
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EXTENSIONS
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More terms from Chuck Seggelin (barkeep(AT)plastereddragon.com), Dec 18 2003
Entry revised by njas, Feb 20 2006
More terms from David Wasserman (wasserma(AT)spawar.navy.mil), Feb 14 2006
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