A007523 Primes in A092845 (decimal expansion of Pi written backwards).

3, 13, 51413, 951413, 2951413, 53562951413, 979853562951413

Offset: 1

Author

N. J. A. Sloane and Robert G. Wilson v

Keywords

• base
• nonn

Comments

Next term is probably A092845(711), a 712-digit probable prime (Baillie-Pomerance-Selfridge-Wagstaff test, cf. PARI/GP documentation) beginning 2116599102453... and ending ...62648323979853562951413.

a(8) = A092845(711) is now a proven prime. - Sean A. Irvine, Jan 07 2018

Examples

			51413 is in the list because it is prime and its decimal reversal, 31415, is the first 5 digits of Pi.
		

References

• M. Gardner, Whys and Wherefores, Univ. Chicago Press, 1989, p. 84.
• N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

• Index entries for sequences related to the number Pi
• Shyam Sunder Gupta, Mystery of pi, Exploring the Beauty of Fascinating Numbers, Springer (2025) Ch. 19, 473-497.
• Sean A. Irvine, Primo certificate for primality of a(8)

Crossrefs

Cf. A005042, A092845, A011545.

Programs

Mathematica

Module[{nn=1000,rd},d=RealDigits[Pi,10,nn][[1]];Select[Table[FromDigits[Reverse[Take[d,n]]],{n,nn}],PrimeQ]]  (* Harvey P. Dale, Jul 11 2023 *)

Formula

Equals A000040 intersect A092845.

Extensions

Edited by M. F. Hasler and N. J. A. Sloane, Mar 30 2008

Edited by T. D. Noe, Oct 30 2008