OFFSET
1,2
COMMENTS
n is in the sequence iff n is not prime and R(n)=n-pi(n). There is no further term up to 3670000000.
a(19) > 10^13. Up to that limit, this sequence contains all the numbers k such that R(k) = k - pi(k). - Giovanni Resta, Aug 08 2019
EXAMPLE
548911025 is in the sequence because 548911025 is the 520118945th nonprime natural number.
MATHEMATICA
Do[s = FromDigits[Reverse[IntegerDigits[n]]]; If[ ! PrimeQ[n] && s == n - PrimePi[n], Print[n]], {n, 548911025}]
CROSSREFS
KEYWORD
nonn,base,more
AUTHOR
Farideh Firoozbakht, Dec 12 2004
EXTENSIONS
a(13)-a(18) from Giovanni Resta, Aug 08 2019
STATUS
approved