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

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

Author

Tanya Khovanova, Aug 26 2022

Keywords

• nonn
• base

Comments

Palindromic tetraprimes are A046394.

The corresponding sequence for three distinct primes is A270175.

Examples

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

Crossrefs

Cf. A046394, A270175.

Programs

Mathematica

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

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