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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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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; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| 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
| David W. Wilson, Table of n, a(n) for n=1..10000
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EXAMPLE
| 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
| 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: A073310 A174414 A046929 * A110787 A202338 A139002
Adjacent sequences: A068692 A068693 A068694 * A068696 A068697 A068698
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KEYWORD
| base,easy,nonn
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AUTHOR
| Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Mar 03 2002
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EXTENSIONS
| More terms from Chuck Seggelin (barkeep(AT)plastereddragon.com), Dec 18 2003
Entry revised by N. J. A. Sloane (njas(AT)research.att.com), Feb 20 2006
More terms from David Wasserman (wasserma(AT)spawar.navy.mil), Feb 14 2006
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