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Search: id:A154963
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| A154963 |
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Primes n such that concatenation of n and n-th prime is prime. |
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2
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| 2, 17, 23, 41, 61, 71, 83, 127, 227, 337, 353, 499, 503, 571, 727, 887, 911, 937, 971, 1061, 1427, 1579, 1663, 1693, 1709, 1871, 1877, 1907, 1949, 1973, 2017, 2063, 2081, 2239, 2339, 2393, 2467, 2713, 2797, 2939, 2999, 3181, 3271, 3463, 3643, 3659, 3677
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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Concatenation of prime 2 and second prime 3 is the prime 23, hence 2 is in the sequence. Concatenation of prime 23 and 23rd prime 83 is the prime 2383, hence 23 is in the sequence.
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MATHEMATICA
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A154963 = Select[ Prime[ Range[ 550 ] ], PrimeQ[ FromDigits[ Join[ IntegerDigits[ # ], IntegerDigits[ Prime[ # ] ] ] ] ] & ] (* >From Alonso Delarte (alonso.delarte(AT)gmail.com) Nov 12 2009 *)
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PROGRAM
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(MAGMA) [ p: p in PrimesUpTo(3700) | IsPrime(StringToInteger(IntegerToString(p) cat IntegerToString(NthPrime(p)))) ];
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CROSSREFS
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For the primes indexed by these concatenations, see A155032. In other words, A000040(a(n)) = A155032.
Sequence in context: A094668 A019421 A105901 this_sequence A049562 A107137 A086322
Adjacent sequences: A154960 A154961 A154962 this_sequence A154964 A154965 A154966
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KEYWORD
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nonn,base,easy,less,new
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AUTHOR
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Juri-Stepan Gerasimov (2stepan(AT)rambler.ru), Jan 18 2009
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EXTENSIONS
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Edited and extended beyond a(3) by Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), Jan 20 2009
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