OFFSET
1,1
COMMENTS
REFERENCES
Andrzej Rotkiewicz, Sur les nombres pseudopremiers pentagonaux, Bull. Soc. Roy. Sci. Liège, Vol. 33 (1964), pp. 261-263.
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
EXAMPLE
7957 = (3*73^2 - 73)/2 is in the sequence since it is pentagonal, composite, and 2^7956 == 1 (mod 7957).
MATHEMATICA
p[n_]:=(3n^2-n)/2; Select[p[Range[3, 10^4]], PowerMod[2, (# - 1), #]==1 &]
CROSSREFS
KEYWORD
nonn
AUTHOR
Amiram Eldar, Oct 13 2017
STATUS
approved