A081509 - OEIS

%I #16 Mar 26 2019 16:20:33

%S 13,366993409,789800591806169089,

%T 8145612997113849913833354347764846494983651329

%N Primes of the form 1 + 2^k + 4^k + 6^k.

%C a(5) has 311 digits. - _Harvey P. Dale_, Mar 18 2019

%C Using the above, a(5) = 1 + 2^399 + 4^399 + 6^399. - _David A. Corneth_, Mar 18 2019

%e n=1: 1 + 2 + 4 + 6 = 13 is 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[Table[1+2^n+4^n+6^n,{n,60}],PrimeQ] (* _Harvey P. Dale_, Mar 18 2019 *)

%Y Cf. A081510.

%K nonn

%O 1,1

%A _Labos Elemer_, Apr 15 2003