A227890 - OEIS

%I #15 Jan 22 2017 17:46:47

%S 3,7,163,353,5021,12739,32719,49681,52391,78901,113501,252913,361091,

%T 452807,551917,993841,1559797,1956979,2193127,3463037,4067983,5003837,

%U 5138953,6115363,6723271,7251857,7447043,7578607,8426989,9479801,11295847,12186593,12439237

%N Primes of the form prime(k)^2 - k.

%H K. D. Bajpai, <a href="/A227890/b227890.txt">Table of n, a(n) for n = 1..7200</a>

%e a(3)= 163: prime(6)^2 - 6= 13^2 - 6= 169 - 6= 163 which is prime.

%e a(4)= 353: prime(8)^2 - 8= 19^2 - 8= 361 - 8= 353 which is prime.

%p with(numtheory):KD := proc() local a; a:= (ithprime(k)^2-k); if isprime(a) then RETURN (a); fi; end: seq(KD(), k=1..1000);

%t Select[Table[Prime[k]^2-k,{k,1000}],PrimeQ]

%o (PARI) for(k=1, 10^5, if(ispseudoprime(KD=((prime(k)^2-k))), print1(KD", ")));

%Y Cf. A000040 (prime numbers).

%Y Cf. A064713 (for the integers k).

%Y Cf. A184935 (primes: k^2 + prime(k)).

%Y Cf. A188831 (primes: k^2 - prime(k)).

%Y Cf. A229203 (primes: k^3 - prime(k)).

%K nonn

%O 1,1

%A _K. D. Bajpai_, Oct 26 2013