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Search: id:A152242
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| A152242 |
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Integers formed by concatenating primes. |
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+0
11
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| 2, 3, 5, 7, 11, 13, 17, 19, 22, 23, 25, 27, 29, 31, 32, 33, 35, 37, 41, 43, 47, 52, 53, 55, 57, 59, 61, 67, 71, 72, 73, 75, 77, 79, 83, 89, 97, 101, 103, 107, 109, 112, 113, 115, 117, 127, 131, 132, 133, 135, 137, 139, 149, 151, 157, 163, 167, 172, 173, 175, 177, 179
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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101 is a member since it is prime; 303 is not since it is composite and 30 is also not a prime.
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PROGRAM
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(PARI) is_A152242(n)={ /* If n is even, the last digit must be 2 and [n\10] (if nonzero) must be in this sequence. (This check is not necessary but improves speed.) */ bittest(n, 0) | return( n%10==2 & (n<10 | is_A152242(n\10))); isprime(n) & return(1); for(i=1, #Str(n)-1, n%10^i>10^(i-1) & isprime( n%10^i ) & is_A152242( n\10^i) & return(1)) } \\ [From M. F. Hasler (MHasler(AT)univ-ag.fr), Oct 15 2009]
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CROSSREFS
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Cf. A105184, A019549, A129800.
Cf. A038692 Square numbers that are concatenations of two or more prime numbers. [From Zak Seidov (zakseidov(AT)yahoo.com), Oct 15 2009]
Sequence in context: A152073 A117289 A106317 this_sequence A166504 A095405 A113581
Adjacent sequences: A152239 A152240 A152241 this_sequence A152243 A152244 A152245
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KEYWORD
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nonn,base
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AUTHOR
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Eric Angelini, Oct 15 2009
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EXTENSIONS
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More terms from M. F. Hasler (MHasler(AT)univ-ag.fr) and Zak Seidov (zakseidov(AT)yahoo.com), Oct 15 2009
PARI code modified to disallow leading zeros. - M. F. Hasler (MHasler(AT)univ-ag.fr), Oct 16 2009
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