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A068811
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Numbers n such that n and its 10's complement are both primes, i.e. n and 10^k - n where k is the number of digits in n, are primes.
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3
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3, 5, 7, 11, 17, 29, 41, 47, 53, 59, 71, 83, 89, 97, 113, 137, 173, 179, 191, 227, 239, 257, 281, 317, 347, 353, 359, 383, 401, 431, 443, 479, 491, 509, 521, 557, 569, 599, 617, 641, 647, 653, 683, 719, 743, 761, 773, 809, 821, 827, 863, 887, 911, 929, 941
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| In other words, primes p such that the difference between the smallest power of 10 exceeding p and p is prime. - Zak Seidov (zakseidov(AT)yahoo.com), Feb 27 2004
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EXAMPLE
| 47 is a prime; the smallest power of 10 exceeding 47 is 100 and 100 - 47 = 53 is prime. Therefore 47 is in the sequence.
641 is a term as 641 and 1000-641 = 359 are primes.
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MATHEMATICA
| Select[Prime[Range[160]], PrimeQ[10^(Floor[Log[10, # ]] + 1) - # ] &] - Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Jun 15 2007
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CROSSREFS
| Sequence in context: A091567 A076186 A092564 * A088083 A116457 A037155
Adjacent sequences: A068808 A068809 A068810 * A068812 A068813 A068814
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KEYWORD
| easy,nonn
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AUTHOR
| Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Mar 07 2002
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EXTENSIONS
| Corrected by Jason Earls (zevi_35711(AT)yahoo.com), May 25 2002
Edited by N. J. A. Sloane (njas(AT)research.att.com), Sep 18 2008 at the suggestion of R. J. Mathar.
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