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%I #18 Aug 11 2024 08:53:34
%S 1,11,23,59,399,63321
%N Numbers k such that 1 + 2^k + 4^k + 6^k is prime.
%e m=1: 1+2+4+6=13 prime.
%t Do[s=1^w+2^w+4^w+6^w; If[IntegerQ[w/100], Print[{w}]]; If[PrimeQ[s], Print[{w, s}]], {w, 0, 1000}]
%t Select[Range[400],PrimeQ[2^#+4^#+6^#+1]&] (* _Harvey P. Dale_, Jun 03 2023 *)
%o (PARI) is(n)=ispseudoprime(1+2^n+4^n+6^n) \\ _Charles R Greathouse IV_, Jun 13 2017
%Y Cf. A081509.
%K more,nonn
%O 1,2
%A _Labos Elemer_, Apr 15 2003
%E a(6) from _Michael S. Branicky_, Aug 10 2024