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A356767 Tetraprimes (products of four distinct primes) whose reversals are different tetraprimes. 0
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 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Palindromic tetraprimes are A046394.
The corresponding sequence for three distinct primes is A270175.
LINKS
EXAMPLE
1518 = 2*3*11*23 is a tetraprime. Its reversal 8151 = 3*11*13*19 is another tetraprime. Thus, 1518 is in this sequence.
MATHEMATICA
Select[Range[10000], Transpose[ FactorInteger[FromDigits[Reverse[IntegerDigits[#]]]]][[2]] == {1, 1, 1, 1} && IntegerDigits[#] != Reverse[IntegerDigits[#]] && Transpose[FactorInteger[#]][[2]] == {1, 1, 1, 1} &]
PROG
(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)
print([k for k in range(9000) if ok(k)]) # Michael S. Branicky, Aug 27 2022
CROSSREFS
Sequence in context: A257753 A236724 A206654 * A112641 A203386 A157375
KEYWORD
nonn,base
AUTHOR
Tanya Khovanova, Aug 26 2022
STATUS
approved

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Last modified March 29 02:16 EDT 2024. Contains 371264 sequences. (Running on oeis4.)