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A065821
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a(n) is the first prime ending in exactly n 1's.
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9
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31, 11, 2111, 101111, 311111, 29111111, 61111111, 1711111111, 14111111111, 31111111111, 311111111111, 2111111111111, 31111111111111, 3511111111111111, 5111111111111111, 101111111111111111, 3511111111111111111
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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LINKS
| Harry J. Smith, Table of n, a(n) for n=1,...,100
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EXAMPLE
| a(4) = 101111 because 1111=11*101, 21111=3*31*227, 31111=53*587, 41111=7^2*829, 51111=3^4*631, 61111=23*2657, 71111=17*47*89, 81111=3*19*1423, 91111=179*509 so 101111 is the first prime ending in four 1's.
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PROG
| (PARI) { b=0; f=1; for (n=1, 100, b=10*b + 1; f*=10; k=0; while (!isprime(b + k*f), if (k%10, k++, k+=2)); write("b065821.txt", n, " ", b + k*f) ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Nov 01 2009]
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CROSSREFS
| Cf. A037055, A065584, A065580, A065581, A065582.
Sequence in context: A040935 A145584 A178561 * A040934 A107114 A077397
Adjacent sequences: A065818 A065819 A065820 * A065822 A065823 A065824
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KEYWORD
| base,nonn
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AUTHOR
| Jonathan Ayres (jonathan.ayres(AT)btinternet.com), Nov 23 2001
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EXTENSIONS
| Edited and extended by Robert G. Wilson v (rgwv(AT)rgwv.com), Jul 04 2003
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