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A115564
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Least number d such that 10^n -/+ d form a prime pair.
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3
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3, 3, 9, 69, 129, 39, 261, 213, 459, 33, 57, 39, 267, 657, 357, 1377, 3, 387, 1899, 393, 213, 651, 327, 3, 2733, 3423, 1533, 429, 603, 1131, 1137, 1113, 1131, 249, 603, 2979, 159, 429, 921, 1269, 2757, 777, 789, 2277, 11799, 9, 5343, 1821, 6981, 23049, 1623
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| a(n)== 0 (mod 3). - Robert G. Wilson v (rgwv(at)rgwv.com), Mar 13 2006
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EXAMPLE
| a(1)=3 because 10-3=7 and 10+3=13 both of which are primes.
a(3)=9 because 1000-9=991 and 1000+9=1009 both of which are primes.
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MATHEMATICA
| f[n_] := Block[{k = 1}, While[ ! PrimeQ[10^n - 3k] || ! PrimeQ[10^n + 3k], k++ ]; 3k]; Array[f, 50]
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PROG
| (PARI) { for (n = 1, 80, tenp = 10^n ; p = nextprime(tenp) ; while ( p-tenp < tenp, diff=p-tenp ; if ( isprime(tenp-diff), print1(diff", ") ; break ; ) ; p=nextprime(p+1) ; ) ; ) } - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Mar 15 2006
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CROSSREFS
| Cf. A113213, A117738.
Sequence in context: A100239 A038080 A190960 * A122961 A165421 A100731
Adjacent sequences: A115561 A115562 A115563 * A115565 A115566 A115567
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KEYWORD
| nonn
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AUTHOR
| Lekraj Beedassy (blekraj(AT)yahoo.com), Mar 11 2006
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EXTENSIONS
| More terms from Craig Baribault (csb166(AT)psu.edu) and Robert G. Wilson v (rgwv(at)rgwv.com), Mar 13 2006
More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Mar 15 2006
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