OFFSET
1,1
COMMENTS
LINKS
Giovanni Resta, Table of n, a(n) for n = 1..200
EXAMPLE
tau(9^9) = tau(387420489) = 19 (prime).
MATHEMATICA
mx = 10^200; Union@ Flatten@ Reap[ Sow[2^ Select[ Range@ Log2[mx], PrimeQ[1 + # 2^#] &]]; Do[ If[ PrimeQ[1 + q p^q], Sow[p^q]], {p, Prime@ Range@ PrimePi@ 34}, {q, 2, Log[p, mx], 2}]; Do[ Sow@ (Select[ Prime@ Range[2, PrimePi[ mx^(1/e)]], PrimeQ[1 + e #^e] &]^e), {e, 34, Floor@Log[31, mx], 2}]][[2, 1]] (* all the 231 terms < 10^200, Giovanni Resta, Mar 07 2017 *)
PROG
(Magma) [n: n in [1..500] | IsPrime(NumberOfDivisors(n^n))]
(PARI) isok(n) = isprime(numdiv(n^n)); \\ Michel Marcus, Mar 07 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, Mar 07 2017
EXTENSIONS
a(4)-a(9) from Giovanni Resta, Mar 07 2017
STATUS
approved