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A246801
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Primes of the form: concatenation n with n-th composite integer.
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2
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4057, 4463, 4969, 5881, 6691, 86117, 90121, 129169, 131171, 136177, 160207, 162209, 169217, 193247, 225287, 252319, 265333, 272341, 280351, 288361, 297371, 327407, 346429, 355441, 388481, 410507, 429529, 451553, 456559, 474581
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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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4057 is in the sequence since 40th composite integer is 57 and 4057 is prime.
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MATHEMATICA
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w = Select[Range[2, 800], ! PrimeQ[#] &]; Select[
Table[FromDigits[Flatten[{IntegerDigits[n], IntegerDigits[w[[n]]]}]], {n, 480}], PrimeQ]
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PROG
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(Python)
import sympy
from sympy import isprime
c = 0
for n in range(2, 10**5):
..if not isprime(n):
....c += 1
....p = str(c)+str(n)
....if isprime(p):
......print(int(p), end=', ')
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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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STATUS
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approved
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