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A100415

Numbers n such that n is R(n)-th nonprime number, where R(n) is the digit reversal of n (A018252(A004086(n))=n).

1, 64, 524, 534, 58725, 907538, 6264385, 9438088, 9596598, 27895162, 422984004, 548911025, 8804661048, 49640253574, 63899981216, 95138721219, 97895906839, 469449672154

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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

LINKS

Table of n, a(n) for n=1..18.

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

Cf. A018252, A004086, A100413, A100414, A114926.

Sequence in context: A382166 A066430 A115740 * A200841 A247929 A183779

Adjacent sequences: A100412 A100413 A100414 * A100416 A100417 A100418

KEYWORD

nonn,base,more

AUTHOR

Farideh Firoozbakht, Dec 12 2004

EXTENSIONS

a(13)-a(18) from Giovanni Resta, Aug 08 2019

STATUS

approved

URL: https://oeis.org/A100415

⇱ A100415 - OEIS