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A109612
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Numbers n such that the string 44n is prime.
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1
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3, 9, 21, 23, 41, 47, 51, 57, 63, 81, 83, 93, 101, 111, 119, 123, 129, 131, 159, 171, 179, 189, 201, 203, 207, 221, 249, 257, 263, 267, 269, 273, 279, 281, 293, 351, 357, 371, 381, 383, 389, 417, 449, 453, 483, 491, 497, 501, 507, 519, 531, 533, 537, 543, 549
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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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If n=3 then 44n = 443 which is a prime.
If n=81 then 44n = 4481 which is a prime.
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MAPLE
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a:= proc(n) local k; for k from 1 +`if`(n=1, 0, a(n-1))
while not isprime(parse( "" ||44||k)) do od; a(n):=k
end:
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MATHEMATICA
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Select[Range[700], PrimeQ[44 10^IntegerLength[#] + #] &] (*Vincenzo Librandi,Jul 30 2014 *)
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PROG
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(Magma) [n: n in [1..600] | IsPrime(Seqint(Intseq(n) cat [4, 4])) ]; //Vincenzo Librandi,Jul 30 2014
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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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EXTENSIONS
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STATUS
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approved
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