OFFSET
1,1
COMMENTS
The corresponding primes p = prime(a(n)) are listed in A121877.
The corresponding primes of the form (5^p - 3^p)/2 are listed in A123705.
a(13) is greater than 1000. - Farideh Firoozbakht, Oct 11 2006
FORMULA
a(n) = primepi(A121877(n)).
MATHEMATICA
Do[If[PrimeQ[(5^Prime[n] - 3^Prime[n])/2], Print[n]], {n, 1000}] (* Robert G. Wilson v, Jan 12 2007 *)
PrimePi[#]&/@Select[Prime[Range[1000]], PrimeQ[(5^#-3^#)/2]&] (* Harvey P. Dale, Sep 23 2018 *)
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Alexander Adamchuk, Oct 08 2006
EXTENSIONS
More terms from Farideh Firoozbakht, Oct 11 2006
a(13)-a(16) computed from A121877 by Jinyuan Wang, Mar 23 2020
a(17)-a(19) from Kellen Shenton, May 18 2022
a(20) from Amiram Eldar, Sep 06 2024
STATUS
approved