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A083969
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Numbers n such that 2.n.3.n.5.n.7.n.11 is prime (dot means concatenation).
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5
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4, 18, 33, 42, 43, 57, 73, 76, 78, 87, 91, 93, 97, 102, 112, 114, 120, 141, 151, 177, 186, 193, 196, 219, 261, 267, 276, 280, 300, 307, 318, 322, 342, 352, 364, 366, 402, 435, 438, 445, 457, 462, 468, 484, 511, 580, 582, 633, 646, 651, 679, 706, 745, 774, 783
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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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2.4.3.4.5.4.7.4.11 = 2434547411, which is prime. Hence 4 is in the sequence.
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MATHEMATICA
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v={}; Do[If[PrimeQ[FromDigits[Join[{2}, IntegerDigits[n], {3}, IntegerDigits[n], {5}, IntegerDigits[n], {7}, IntegerDigits[n], {1, 1}]]], v=Append[v, n]], {n, 1000}]; v
Select[Range[660], PrimeQ[FromDigits[Join[{2}, IntegerDigits[ # ], {3}, IntegerDigits[ # ], {5}, IntegerDigits[ # ], {7}, IntegerDigits[ # ], {1, 1}]]] &] (* Stefan Steinerberger, Jun 28 2007 *)
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PROG
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(Python)
from sympy import isprime
def aupton(terms):
n, alst = 1, []
while len(alst) < terms:
s = str(n)
t = int('2'+s+'3'+s+'5'+s+'7'+s+'11')
if isprime(t): alst.append(n)
n += 1
return alst
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CROSSREFS
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KEYWORD
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base,easy,nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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