|
| |
|
|
A099078
|
|
Numbers n such that pi(n).pi(n-1) ... pi(3).pi(2) is prime (dot between numbers means concatenation).
|
|
3
|
| |
|
|
|
OFFSET
|
1,1
|
|
|
COMMENTS
|
Number of digits of primes corresponding to the five known terms of this sequence are respectively 4,21,67,605,1633.
|
|
|
LINKS
|
Table of n, a(n) for n=1..6.
C. Rivera, ,Primes by Listing, The Prime Puzzles & Problems connection.
Eric Weisstein ,A Section of The World of Mathematics
|
|
|
EXAMPLE
|
5 is in the sequence because pi(5).pi(4).pi(3).pi(2)=3221 is prime.
|
|
|
MATHEMATICA
|
s = ""; Do[s = ToString[PrimePi[n]] <> s; k = ToExpression[s]; If[PrimeQ[k], Print[n]], {n, 2, 5235}] (Propper)
|
|
|
CROSSREFS
|
Cf. A046035, A099077, A099079, A099080.
Sequence in context: A085101 A184724 A082005 * A049452 A209116 A033445
Adjacent sequences: A099075 A099076 A099077 * A099079 A099080 A099081
|
|
|
KEYWORD
|
base,more,nonn
|
|
|
AUTHOR
|
Farideh Firoozbakht, Oct 23 2004
|
|
|
EXTENSIONS
|
One more term from Ryan Propper (rpropper(AT)stanford.edu), Aug 30 2005
|
|
|
STATUS
|
approved
|
| |
|
|
