A270175 -id:A270175 - cp's OEIS frontend

A271799 Prime numbers whose reversal is a product of 3 distinct primes.

223, 269, 281, 457, 499, 839, 1049, 1289, 1373, 1459, 1543, 1609, 2003, 2011, 2017, 2027, 2029, 2053, 2081, 2087, 2213, 2221, 2237, 2239, 2243, 2267, 2269, 2293, 2297, 2441, 2459, 2609, 2657, 2659, 2693, 2699, 2803, 2833, 2851, 2857, 2879, 2887, 2897, 3449, 3557

Offset: 1

Chai Wah Wu, Apr 14 2016

Each of the three distinct primes must have an exponent of one, i.e., the number of distinct primes and also the number of primes counted with multiplicity must equal three. - Harvey P. Dale, Sep 26 2024

Chai Wah Wu, Table of n, a(n) for n = 1..10000

Cf. A270175, A007304.

Select[Range[4000], PrimeQ[#] && Transpose[FactorInteger[IntegerReverse[#]]][[2]] == {1, 1, 1} &] (* Tanya Khovanova, Mar 16 2021 *)
Select[Prime[Range[500]],PrimeNu[IntegerReverse[#]]==PrimeOmega[IntegerReverse[#]]==3&] (* Harvey P. Dale, Sep 26 2024 *)

A356767 Tetraprimes (products of four distinct primes) whose reversals are different tetraprimes.

Original entry on oeis.org

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

Offset: 1

Tanya Khovanova, Aug 26 2022

Palindromic tetraprimes are A046394.

The corresponding sequence for three distinct primes is A270175.

			1518 = 2*3*11*23 is a tetraprime. Its reversal 8151 = 3*11*13*19 is another tetraprime. Thus, 1518 is in this sequence.

Cf. A046394, A270175.

Select[Range[10000],Transpose[ FactorInteger[FromDigits[Reverse[IntegerDigits[#]]]]][[2]] == {1, 1, 1, 1} && IntegerDigits[#] != Reverse[IntegerDigits[#]] && Transpose[FactorInteger[#]][[2]] == {1, 1, 1, 1} &]

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

cp's OEIS Frontend

A271799 Prime numbers whose reversal is a product of 3 distinct primes.

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