
REFERENCES

A. H. Beiler, Recreations in the Theory of Numbers, Dover, NY, 1964, p. 52.
C. Clawson, Mathematical Mysteries, Plenum Press, 1996, p. 180.
R. Crandall and C. Pomerance, Prime Numbers: A Computational Perspective, Springer, NY, 2001; see p. 29.
G. H. Hardy and E. M. Wright, An Introduction to the Theory of Numbers, 5th ed., Oxford Univ. Press, 1979, th. 80.
P. Ribenboim, The Book of Prime Number Records. SpringerVerlag, NY, 2nd ed., 1989, p. 277.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
I. Vardi, Computational Recreations in Mathematica. AddisonWesley, Redwood City, CA, 1991, p. 73.
D. Wells, The Penguin Dictionary of Curious and Interesting Numbers. Penguin Books, NY, 1986, 163.


LINKS

Table of n, a(n) for n=1..3.
Edgar Costa, Robert Gerbicz, and David Harvey, A search for Wilson primes, arXiv:1209.3436 [math.NT], 2012.
Edgar Costa, Robert Gerbicz, and David Harvey, A search for Wilson primes, Math. Comp. 83 (2014), pp. 30713091.
James Grime and Brady Haran, What do 5, 13 and 563 have in common? (2014)
E. Lehmer, "On congruences involving Bernoulli numbers and the quotients of Fermat and Wilson". Annals of Mathematics 39 (2): 350360 (1938). doi:10.2307/1968791.
Tapio Rajala, Status of a search for Wilson primes
Eric Weisstein's World of Mathematics, Wilson Prime
Eric Weisstein's World of Mathematics, Integer Sequence Primes
Wikipedia, Wilson prime
P. Zimmermann, Records for prime numbers


PROG

(PARI) forprime(n=2, 10^9, if(Mod((n1)!, n^2)==1, print1(n, ", "))) \\ Felix FrÃ¶hlich, Apr 28 2014
(PARI) is(n)=prod(k=2, n1, k, Mod(1, n^2))==1 \\ Charles R Greathouse IV, Aug 03 2014
(Python)
from sympy import prime
A007540_list = []
for n in range(1, 10**4):
....p, m = prime(n), 1
....p2 = p*p
....for i in range(2, p):
........m = (m*i) % p2
....if m == p21:
........A007540_list.append(p) # Chai Wah Wu, Dec 04 2014
