

A100003


Prime numbers p such that the concatenation of all odd primes up through p in decreasing order is prime.


6




OFFSET

1,1


COMMENTS

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.


LINKS



EXAMPLE

17 is in the sequence because 17.13.11.7.5.3 is prime (dot between numbers means concatenation).


MATHEMATICA

Do[If[PrimeQ[(v={}; Do[v=Join[v, IntegerDigits[Prime[nj+1]]], {j, n1}]; 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 *)


CROSSREFS



KEYWORD

base,more,nonn,nice


AUTHOR



STATUS

approved



