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A156770
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1 then least greater integer such that concatenate a(n-1),a(n) is prime.
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1
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1, 3, 7, 9, 11, 17, 21, 29, 39, 43, 49, 51, 53, 81, 91, 99, 103, 123, 127, 133, 153, 191, 227, 231, 241, 249, 253, 273, 281, 291, 293, 311, 323, 333, 337, 339, 341, 347, 359, 377, 387, 397, 427, 429, 431, 441, 443, 453, 461, 467, 471, 481, 489, 493, 523, 541
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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LINKS
| Paolo P. Lava, Table of n, a(n) for n = 1..10000
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EXAMPLE
| 17, 21 are in as 1721 is first prime greater than 1717.
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MAPLE
| cat2 := proc(a, b) a*10^(max(1, ilog10(b)+1))+b ; end: A156770 := proc(n) option remember ; local a; if n = 1 then 1; else for a from procname(n-1)+1 do if isprime( cat2(procname(n-1), a) ) then RETURN(a) ; fi; od: fi; end: seq(A156770(n), n=1..80) ; [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Feb 20 2009]
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CROSSREFS
| Sequence in context: A186890 A075607 A173699 * A088630 A129747 A004614
Adjacent sequences: A156767 A156768 A156769 * A156771 A156772 A156773
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KEYWORD
| nonn,base
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AUTHOR
| Gerald Hillier (adr.rabbicat(AT)gmail.com), Feb 15 2009, mar 13 2010
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EXTENSIONS
| More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Feb 20 2009
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