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A086101
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Concatenation of the last digit of p(n) and of the first digit of prime(n+1) gives prime; values of such n in the sequence.
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1
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1, 4, 5, 6, 7, 11, 20, 21, 25, 26, 27, 28, 30, 31, 32, 33, 36, 37, 38, 39, 40, 42, 43, 44, 45, 63, 64, 66, 67, 68, 69, 73, 125, 126, 127, 128, 130, 131, 132, 133, 135, 136, 137, 154, 155, 156, 159, 160, 161, 163, 164, 165, 167, 168, 170, 172, 173, 174, 177, 178, 179
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| There are roughly 5/(18n log 10) * 10^n members of this sequence up to 10^n: all primes between 10^k and 2*10^k, half the primes between 3*10^k and 4*10^k, 3/5 of the primes between 7*10^k and 8*10^k, and 1/4 of the primes between 9*10^k and 10*10^k for all 1 < k < n, using the prime number theorem in arithmetic progressions. Thus the 'probability' that a random number up to 10^n is in this sequence is 0.12/n.
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EXAMPLE
| a(7)=20 because prime{20)=71, prime{21)=73 and 17 is prime.
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CROSSREFS
| Sequence in context: A191164 A004714 A014098 * A131260 A047566 A037355
Adjacent sequences: A086098 A086099 A086100 * A086102 A086103 A086104
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KEYWORD
| easy,nonn,base
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AUTHOR
| Zak Seidov (zakseidov(AT)yahoo.com), Jul 09 2003
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EXTENSIONS
| Comment from Charles R Greathouse IV (charles.greathouse(AT)case.edu), Apr 27 2010
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