The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.



(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A100003 Prime numbers n such that the concatenation of all odd primes up through n in decreasing order is prime. 6
3, 5, 17, 89, 383, 8831 (list; graph; refs; listen; history; text; internal format)



Next term is greater than 4400th prime and the prime corresponding to the next term has more than 20000 digits. Number of digits of primes corresponding to the six known terms of the sequence are respectively 1, 2, 9, 43, 198, 4202.

We can see the prime corresponding to 383 (the 5th term of the sequence) in the page related to puzzle 8 of the website of Carlos Rivera.

a(7) > prime(28800) = 335033. - Giovanni Resta, Apr 01 2013


Table of n, a(n) for n=1..6.

C. Rivera, Primes by Listing.


17 is in the sequence because is prime (dot between numbers means concatenation).


Do[If[PrimeQ[(v={}; Do[v=Join[v, IntegerDigits[Prime[n-j+1]]], {j, n-1}]; FromDigits[v])], Print[Prime[n]]], {n, 2, 4413}]

Prime[#]&/@Select[Range[100], PrimeQ[FromDigits[Flatten[IntegerDigits/@ Prime[Range[#, 2, -1]]]]]&] (* To generate a(6) increase the Range by 1000, but the program will run a long time. *) (* Harvey P. Dale, Nov 27 2015 *)


Cf. A046284, A099070, A099071, A099073.

The actual prime concatenations in A092448 and the original concatenations in A092447. - Dmitry Kamenetsky, Mar 02 2009

Sequence in context: A227335 A281627 A102846 * A283331 A114161 A302199

Adjacent sequences:  A100000 A100001 A100002 * A100004 A100005 A100006




Farideh Firoozbakht, Nov 06 2004



Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified August 14 04:13 EDT 2020. Contains 336477 sequences. (Running on oeis4.)