Tau Function Prime

tau(n) is prime for n=63001, 458329, 942841, 966289, 1510441, ... (OEIS A135430). These values are also known as Lehmer-Ramanujan numbers or LR numbers since the first of them was found by Lehmer (1965). The corresponding primes have explicit values given by -80561663527802406257321747, -11695495424911987900947041440697, ... (OEIS A265913).

It is known that if tau(n) is prime, then n must be an odd square.

Large values of n for which tau(n) is a (probable) prime are summarized in the table below (Lifchitz and Lifchitz).

tau(n)decimal digitsdiscoverer
tau(643^(11688))180524N. Lygeros and O. Rozier (May 2015)
tau(971^(15738))258571N. Lygeros and O. Rozier (May 2015)
tau(509^(18946))282048N. Lygeros and O. Rozier (May 2015)
tau(631^(32370))498503N. Lygeros and O. Rozier (May 2015)
tau(773^(34960))555339N. Lygeros and O. Rozier (Sep. 2015)

See also

Integer Sequence Primes, Tau Function

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Lehmer, D. H. "The Primality of Ramanujan's Tau-Function." Amer. Math. Monthly 72, 15-18, 1965.Lifchitz, H. and Lifchitz, R. "PRP Records: Probable Primes Top 10000.", N. J. A. Sequences A135430 and A265913 in "The On-Line Encyclopedia of Integer Sequences."

Cite this as:

Weisstein, Eric W. "Tau Function Prime." From MathWorld--A Wolfram Web Resource.

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