A242092 Numbers n such that n and the digital reversal of the n-th prime in base 10 have the same distinct prime factors.

86, 1357, 24146, 1028736826, 33667786628, 2132089369082

Offset: 1

Author

Chai Wah Wu, Aug 14 2014

Keywords

• nonn
• base
• more
• hard

Comments

First 3 terms are all products of 2 primes.

a(4) > 10^8. - Chai Wah Wu, Aug 15 2014

a(7) > 10^13. - Giovanni Resta, Dec 09 2019

Examples

			86 = 2^1*43^1, the 86th prime is 443 and 344 = 2^3*43^1.
1357 = 59^1*23^1, the 1357th prime is 11213 and 31211 = 59^1*23^2.
		

Crossrefs

Cf. A110751.

Programs

PARI

rev(n)=r="";d=digits(n);for(i=1,#d,r=concat(Str(d[i]),r));eval(r)
for(n=1,10^7,p=rev(prime(n));if(omega(n)==omega(p),if(gcd(n,p)==min(n,p),print1(n,", ")))) \\ Derek Orr, Aug 14 2014

Python

from sympy import primefactors, prime
A242092 = [n for n in range(1,10**7) if primefactors(n) == primefactors(int(str(prime(n))[::-1]))]

Extensions

a(4)-a(6) from Giovanni Resta, Dec 09 2019