login
Primes of the form p^2 - p*q + q^2, where p and q are consecutive primes.
3

%I #42 May 06 2022 13:13:51

%S 7,19,3163,23743,28927,70783,141403,198943,223837,265333,283267,

%T 329503,1136383,1223263,1254427,1488427,2238043,2421163,3625243,

%U 3904603,4709143,4884127,5216683,5784133,7376683,8065627,8797183,10660333,11242717,12348223,16613803,18594019,19202167,19999027

%N Primes of the form p^2 - p*q + q^2, where p and q are consecutive primes.

%H David A. Corneth, <a href="/A339698/b339698.txt">Table of n, a(n) for n = 1..10000</a> (first 100 terms from Zak Seidov)

%e a(2) = 19 = 3^2 - 3*5 + 5^2 is the only prime obtained with a pair of twin primes: (3, 5). - _Bernard Schott_, Dec 23 2020

%t Select[Map[#1^2 - #1 #2 + #2^2 & @@ # &, Partition[Prime@ Range[610], 2, 1]], PrimeQ] (* _Michael De Vlieger_, Dec 13 2020 *)

%o (PARI) forprime(p=1, 1e4, my(q=nextprime(p+1), x=p^2-p*q+q^2); if(ispseudoprime(x), print1(x, ", "))) \\ _Felix Fröhlich_, Dec 14 2020

%o (PARI) first(n) = { my(q = 2, p, res = vector(n), t = 0); forprime(p = 3, oo, c = p^2 - p*q + q^2; if(isprime(c), t++; res[t] = c; if(t >= n, return(res) ) ); q = p; ) } \\ _David A. Corneth_, Dec 19 2020

%Y Cf. A243761 (similar, with p^2 + p*q + q^2), A339920 (the primes p).

%K nonn

%O 1,1

%A _Zak Seidov_, Dec 13 2020