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Search: id:A030457
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| A030457 |
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Numbers n such that n concatenated with n+1 is prime. |
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+0
3
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| 2, 6, 8, 12, 36, 42, 50, 56, 62, 68, 78, 80, 90, 92, 96, 102, 108, 120, 126, 138, 150, 156, 180, 186, 188, 192, 200, 216, 242, 246, 252, 270, 276, 278, 300, 308, 312, 318, 330, 338, 342, 350, 362, 368, 378, 390, 402, 410, 416, 420, 426, 428, 432
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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E.g. 1213 is prime.
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MAPLE
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concat:=proc(a, b) local bb: bb:=nops(convert(b, base, 10)): 10^bb*a+b end proc: a:=proc(n) if isprime(concat(n, n+1))=true then n else end if end proc: seq(a(n), n=0..500); - Emeric Deutsch (deutsch(AT)duke.poly.edu), Nov 23 2007
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CROSSREFS
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Cf. A030458, A054211, A052089, A052087, A052088.
Adjacent sequences: A030454 A030455 A030456 this_sequence A030458 A030459 A030460
Sequence in context: A082473 A113462 A065392 this_sequence A054248 A038108 A087327
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KEYWORD
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nonn,base,nice
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AUTHOR
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Patrick De Geest (pdg(AT)worldofnumbers.com)
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