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A356767
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Tetraprimes (products of four distinct primes) whose reversals are different tetraprimes.
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0
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1518, 2046, 2226, 2262, 2418, 2478, 2618, 2622, 2814, 2838, 2886, 3135, 3927, 4170, 4182, 4386, 4389, 4746, 4785, 4935, 5313, 5394, 5406, 5478, 5565, 5655, 5838, 5874, 6018, 6045, 6222, 6402, 6438, 6474, 6486, 6690, 6699, 6834, 6846, 6882, 7293, 7458, 8106, 8142
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OFFSET
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1,1
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COMMENTS
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Palindromic tetraprimes are A046394.
The corresponding sequence for three distinct primes is A270175.
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LINKS
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EXAMPLE
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1518 = 2*3*11*23 is a tetraprime. Its reversal 8151 = 3*11*13*19 is another tetraprime. Thus, 1518 is in this sequence.
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MATHEMATICA
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Select[Range[10000], Transpose[ FactorInteger[FromDigits[Reverse[IntegerDigits[#]]]]][[2]] == {1, 1, 1, 1} && IntegerDigits[#] != Reverse[IntegerDigits[#]] && Transpose[FactorInteger[#]][[2]] == {1, 1, 1, 1} &]
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PROG
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(Python)
from sympy import factorint
def tetra(n): return list(factorint(n).values()) == [1, 1, 1, 1]
def ok(n):
if not tetra(n): return False
revn = int(str(n)[::-1])
return n != revn and tetra(revn)
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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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