A039954 Palindromic primes formed from the reflected decimal expansion of Pi.

3, 313, 31415926535897932384626433833462648323979853562951413

Offset: 1

Author

G. L. Honaker, Jr.

Keywords

• base
• nonn
• bref

Comments

Carlos Rivera reports that the next two members of this sequence have 301 and 921 digits. The first has been tested with APRTE-CLE. The second one is only a StrongPseudoPrime at the moment. - May 16 2003

Thomas Spahni reports that the fifth member of this sequence with 921 digits is prime. He used Francois Morain's ECPP-V6.4.5a which proved primality in 14913.7 seconds running on a Celeron Core2 CPU at 2.00GHz. - Jun 05 2008

Primes in A135697. Terms with an odd number of digits are the primes in A135698. - Omar E. Pol, Mar 06 2012

Links

• C. K. Caldwell and G. L. Honaker, Jr., Prime Curios!, 31414...51413 (53-digits)
• Shyam Sunder Gupta, Mystery of pi, Exploring the Beauty of Fascinating Numbers, Springer (2025) Ch. 19, 473-497.
• Eric Weisstein's World of Mathematics, Palindromic Prime.

Crossrefs

Cf. A002385, A119351, A135697, A135698.

Programs

Mathematica

Select[Table[p = Flatten[RealDigits[Pi, 10, d]]; (FromDigits[p] - 1)*10^(Length[p] - 3) + FromDigits[Drop[Reverse[p], 2]], {d, 27}], PrimeQ] (* Arkadiusz Wesolowski, Dec 18 2011 *)