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A242092 Numbers n such that n and the digital reversal of the n-th prime in base 10 have the same distinct prime factors. 1
86, 1357, 24146, 1028736826, 33667786628, 2132089369082 (list; graph; refs; listen; history; text; internal format)
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

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Last modified August 10 20:21 EDT 2022. Contains 356039 sequences. (Running on oeis4.)