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A019549
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Primes formed by concatenating other primes.
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12
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23, 37, 53, 73, 113, 137, 173, 193, 197, 211, 223, 227, 229, 233, 241, 257, 271, 277, 283, 293, 311, 313, 317, 331, 337, 347, 353, 359, 367, 373, 379, 383, 389, 397, 433, 523, 541, 547, 557, 571, 577, 593, 613, 617, 673, 677, 719, 727, 733, 743, 757, 761, 773, 797, 977
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OFFSET
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1,1
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LINKS
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EXAMPLE
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113 is member as 11 and 3 are primes.
a(12)=227 = "2"+"2"+"7" is the first term not in A105184 (restricted to concatenation of two primes). [M. F. Hasler, Oct 15 2009]
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PROG
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(PARI) is_A019549(n, recurse=0)={ isprime(n) == recurse & return(recurse); for(i=1, #Str(n)-1, isprime( n%10^i ) & is_A019549( n\10^i, 1) & n\10^(i-1)%10 & return(1)) } \\ M. F. Hasler, Oct 15 2009
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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R. Muller
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STATUS
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approved
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