OFFSET
1,1
COMMENTS
Almost half of the values for k < 100 are primes.
Numbers k such that k^2 - 3k + 1 is a prime. - Jon E. Schoenfield, Dec 22 2017
LINKS
Iain Fox, Table of n, a(n) for n = 1..10000
EXAMPLE
40 is in the sequence because sqrt(40*39*38*37 + 1) is 1481 which is prime.
MATHEMATICA
Select[Range[150], PrimeQ[Sqrt[ #*(# - 1)*(# - 2)*(# - 3) + 1]] &] (* Ray Chandler, Aug 24 2006 *)
Select[Range[150], PrimeQ[#^2-3#+1]&] (* Harvey P. Dale, May 13 2019 *)
PROG
(PARI) isok(k) = isprime(k^2 - 3k + 1); \\ Michel Marcus, Dec 22 2017
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Ben Paul Thurston, Oct 20 2002
EXTENSIONS
Extended by Ray Chandler, Aug 24 2006
STATUS
approved