cp's OEIS Frontend

A246060 Number of primes of the form k^(n - m) - m^k where n > 2 and positive k, m.

%I A246060 #59 Feb 25 2020 10:31:16
%S A246060 1,1,1,5,4,5,4,7,2,8,3,10,1,12,7,13,1,11,6,13,6,19,3,12,4,17,4,10,2,
%T A246060 18,4,15,3,21,6,14,8,18,9,23,7,9,7,21,5,13,6,22,8,16,8,24,5,22,9,12,6,
%U A246060 26,9,26,11,27,5,30,14,34,9,23,9,48,7,11,14,37,8,32
%N A246060 Number of primes of the form k^(n - m) - m^k where n > 2 and positive k, m.
%e A246060 a(3) = 1 because 2^(3 - 1) - 1^2 = 3 is prime with k = 2 and m = 1;
%e A246060 a(4) = 1 because 2^(4 - 1) - 1^2 = 7 is prime with k = 2 and m = 1;
%e A246060 a(5) = 1 because 3^(5 - 2) - 2^3 = 19 is prime with k = 3 and m = 2.
%o A246060 (PARI) a(n) = {my(k=2, q, v=List([])); if(ispseudoprime(q=2^(n-1)-1), listput(v, q)); while(k^(n-2)>2^k, if(ispseudoprime(q=k^(n-2)-2^k), listput(v, q)); k++); for(m=3, n-2, for(t=2, k-1, if(ispseudoprime(q=t^(n-m)-m^t), listput(v, q)))); #Set(v); } \\ _Jinyuan Wang_, Feb 24 2020
%Y A246060 Cf. A242113, A245459.
%K A246060 nonn
%O A246060 3,4
%A A246060 _Juri-Stepan Gerasimov_, Aug 23 2014
%E A246060 Definition and a(7) corrected by _Colin Barker_, Sep 01 2014
%E A246060 More terms from _Jinyuan Wang_, Feb 24 2020