

A282183


Numbers k such that the reverse of the first k digits in the decimal expansion of Pi forms a prime.


0




OFFSET

1,2


COMMENTS

The initial digits of a few corresponding primes are in A007523. The last one a(10)=768556......62951413 is a prime with 13280digit. That is A092845(13279).


LINKS

Table of n, a(n) for n=1..10.


EXAMPLE

1 is a term as the first digit of pi, 3, reversed is prime. 2 is a term as the first two digits of pi, 31, reversed is prime. 3 is not a term as the first three digits of pi, 314, reversed, is not prime.  David A. Corneth, Feb 13 2017


MATHEMATICA

Do[If[PrimeQ[FromDigits[Reverse[IntegerDigits[Floor[Pi*10^(n  1)]]]]], Print[n]], {n, 13335}]
Module[{pid=RealDigits[Pi, 10, 20000][[1]]}, Select[Range[16000], PrimeQ[ FromDigits[ Reverse[Take[pid, #]]]]&]] (* Harvey P. Dale, Sep 06 2019 *)


CROSSREFS

Cf. A092845, A007523, A011545.
Sequence in context: A043329 A023699 A058605 * A103025 A134080 A342792
Adjacent sequences: A282180 A282181 A282182 * A282184 A282185 A282186


KEYWORD

nonn,more,base,less


AUTHOR

XU Pingya, Feb 13 2017


STATUS

approved



