|
%I #13 Jan 29 2019 01:47:29
%S 2,5,7,11,13,16,22,29,43,56,67,83,85,107,317,325,517,1660,2010,2368,
%T 4483,4697
%N Numbers k such that k! - (k-1)! + (k-2)! + 1 is prime.
%e a(11) = 11! - 10! + 9! + 1 = 36650881 (prime).
%e a(16) = 16! - 15! + 14! + 1 = 19702293811201 (prime).
%p a := proc (n) if isprime(factorial(n-2)*((n-1)^2+1)+1) = true then n else end if end proc: seq(a(n), n = 2 .. 700); # _Emeric Deutsch_, Mar 18 2009
%o (PARI) is(n)=ispseudoprime(1+(n^2-2*n+2)*(n-2)!) \\ _Charles R Greathouse IV_, Dec 27 2013
%o (PFGW) ABC2 $a!-($a-1)!+($a-2)!+1
%o a: from 2 to 10000
%o _Charles R Greathouse IV_, Dec 27 2013
%K nonn
%O 1,1
%A _Kyle D. Balliet_, Mar 07 2009
%E More terms from _Emeric Deutsch_, Mar 18 2009
%E a(18)-a(22) from _Charles R Greathouse IV_, Dec 27 2013
|
