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A130112
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Primes prime(n) such that 10*prime(n)+prime(n+2) is not prime.
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0
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2, 19, 23, 29, 31, 37, 43, 47, 53, 59, 61, 71, 73, 79, 83, 97, 103, 107, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 191, 197, 211, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 293, 307, 311, 317, 331, 349, 353, 359, 373, 379, 383, 389
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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EXAMPLE
| a(7)=43 because 10*41+53=483 and 483=3*7*23 is not prime,
a(8)=47 because 10*47+59=529 and 529=23^2 is not prime,
a(9)=53 because 10*53+61=591 and 591=3*197 is not prime, ...
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MAPLE
| ts_p6_02:=proc(n) local a, b, i, ans; ans := [ ]: for i from 1 to n do a := 10*ithprime(i)+ithprime(i+2): if (isprime(a)=false) then ans := [ op(ans), ithprime(i) ]: fi od; RETURN(ans) end: ts_p6_02(300);
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MATHEMATICA
| Transpose[Select[Partition[Prime[Range[200]], 3, 1], !PrimeQ[10First[#]+ Last[#]]&]][[1]] (* From Harvey P. Dale, Jan 04 2012 *)
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CROSSREFS
| Cf. A129900.
Sequence in context: A022119 A042247 A041451 * A019348 A155025 A191068
Adjacent sequences: A130109 A130110 A130111 * A130113 A130114 A130115
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KEYWORD
| nonn
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AUTHOR
| Jani Melik (jani_melik(AT)hotmail.com), Aug 01 2007
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