A007523 - OEIS

A007523

Primes in A092845 (decimal expansion of Pi written backwards).
(Formerly M2966)

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

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

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

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

Table of n, a(n) for n=1..7.

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)

FORMULA

Equals A000040 intersect A092845.

EXAMPLE

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

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 *)

CROSSREFS

Cf. A005042, A092845, A011545.

Sequence in context: A320041 A016104 A112856 * A092830 A317481 A271393

Adjacent sequences: A007520 A007521 A007522 * A007524 A007525 A007526

KEYWORD

base,nonn

AUTHOR

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

EXTENSIONS

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

Edited by T. D. Noe, Oct 30 2008

STATUS

approved