OFFSET
1,1
COMMENTS
The only primes of the form (p^k-1)/2 are A076481, since (p^k-1)/2 is divisible by (p-1)/2.
k must be a power of 2, since if k has an odd divisor d>1, (p^k+1)/2 is divisible by (p^(k/d)+1)/2.
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
a(3) = 41 is in the sequence because 41 = (3^4 + 1)/2.
MAPLE
N:= 10^6: # to get terms <= N
p:= 2:
Res:= NULL:
do
p:= nextprime(p);
if p^2 >= 2*N then break fi;
pk:= p;
do
pk:= pk^2;
if pk >= 2*N then break fi;
v:= (pk+1)/2;
if isprime(v) then Res:= Res, v;
fi;
od
od:
sort([Res]); # Robert Israel, May 27 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
J. M. Bergot and Robert Israel, May 27 2019
STATUS
approved