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A128780 Numbers n such that n^k+(n+1)^k is prime for k = 1, 2, 4.

%I A128780 #10 Mar 29 2017 19:44:18
%S A128780 1,2,9,14,189,204,230,320,680,765,1080,1190,1359,1364,1500,1764,1850,
%T A128780 2049,2115,2360,2379,2919,3050,3110,3179,3579,3794,4164,4215,4470,
%U A128780 5355,5619,5630,5664,5810,5889,5979,6035,6150,6269,6824,6960,7275,8045,8259
%N A128780 Numbers n such that n^k+(n+1)^k is prime for k = 1, 2, 4.
%C A128780 n^k+(n+1)^k is prime only for k = power of 2.
%C A128780 There are 1242 terms < 10^6.
%C A128780 All terms > 2 are congruent to 0 or 4 (mod 5). - _Robert Israel_, Mar 29 2017
%H A128780 Robert Israel, <a href="/A128780/b128780.txt">Table of n, a(n) for n = 1..10000</a>
%e A128780 {2+1, 2^2+3^2,2^4+3^4} = {3,13,97} all prime,
%e A128780 {9+10, 9^2+10^2,9^4+10^4} = {19,181,16561} all prime.
%p A128780 select(n -> isprime(2*n+1) and isprime(2*n^2+2*n+1) and isprime(n^4+(n+1)^4),
%p A128780 [1,2,seq(seq(5*i+j,j=[0,4]),i=1..10000)]); # _Robert Israel_, Mar 29 2017
%t A128780 pnQ[n_]:=And@@PrimeQ/@(n^{1,2,4}+(n+1)^{1,2,4}); Select[Range[9000], pnQ]  (* _Harvey P. Dale_, Apr 06 2011 *)
%Y A128780 Subset of A068501.
%K A128780 nonn
%O A128780 1,2
%A A128780 _Zak Seidov_, Mar 28 2007