A245229 - OEIS

%I #20 Jul 20 2014 16:42:19

%S 7,47,61,103,113,211,223,229,311,337,401,419,491,787,1021,1453,1489,

%T 1697,2039,3659,4703,5279

%N Primes that are the sum of 7 cubes and no fewer.

%C Intersection of A018890 and A000040.

%C If, as is conjectured, the last term of A018890 is 8042, there are no more terms than those shown. - _Robert Israel_, Jul 14 2014

%e a(1) = 7 = 1^3 + 1^3 + 1^3 + 1^3 + 1^3 + 1^3 + 1^3.

%e a(2) = 47 = 3^3 + 2^3 + 2^3 + 1^3 + 1^3 + 1^3 + 1^3.

%e a(3) = 61 = 3^3 + 2^3 + 2^3 + 2^3 + 2^3 + 1^3 + 1^3.

%e a(4) = 103 = 4^3 + 3^3 + 2^3 + 1^3 + 1^3 + 1^3 + 1^3.

%p for n from 1 to 10^4 do

%p   m:= floor(n^(1/3));

%p   if m^3 = n then M[n]:= 1

%p   else

%p     M[n]:= 1 + min(seq(M[n-j^3],j=1..m));

%p   fi

%p od:

%p select(n -> M[n]=7 and isprime(n), [$1..10^4]); # _Robert Israel_, Jul 14 2014

%Y Cf. A000578, A018890, A000040.

%K nonn,less,fini

%O 1,1

%A _Rafael F. Farias_, Jul 13 2014