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

1,1

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

Links

Table of n, a(n) for n=1..6.

Example

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.

Prog

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

Crossrefs

Cf. A110751.

Sequence in context: A034277 A254702 A206615 * A232859 A224259 A223915

Adjacent sequences: A242089 A242090 A242091 * A242093 A242094 A242095

Keyword

nonn,base,more,hard

Author

Chai Wah Wu, Aug 14 2014

Extensions

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

Status

approved