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A239696 Smallest number m such that m and reverse(m) each have n distinct prime factors. 1
2, 6, 66, 858, 6006, 204204, 10444434, 208888680, 6172882716 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

10^11 < a(10) <= 438024420834. - Giovanni Resta, Mar 28 2014

LINKS

Table of n, a(n) for n=1..9.

EXAMPLE

The first nontrivial example is a(6) = 204204. 204204 = 17*2^2*3*7*11*13 (6 distinct prime factors). 402402 = 2*3*7*67*11*13 (6 distinct prime factors). Since 204204 is the smallest number with this property, a(6) = 204204.

PROG

(Python)

import sympy

from sympy import factorint

def Rev(x):

..rev = ''

..for i in str(x):

....rev = i + rev

..return int(rev)

def RevFact(x):

..n = 2

..while n < 10**8:

....if len(list(factorint(n).values())) == x:

......if len(list(factorint(Rev(n)).values())) == x:

........return n

......else:

........n += 1

....else:

......n += 1

x = 1

while x < 50:

..print(RevFact(x))

..x += 1

CROSSREFS

Cf. A046399, A113548.

Sequence in context: A055685 A262047 A280393 * A335645 A082619 A046399

Adjacent sequences:  A239693 A239694 A239695 * A239697 A239698 A239699

KEYWORD

nonn,base,more

AUTHOR

Derek Orr, Mar 24 2014

EXTENSIONS

a(8)-a(9) from Giovanni Resta, Mar 28 2014

STATUS

approved

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Last modified January 28 23:12 EST 2022. Contains 350670 sequences. (Running on oeis4.)