A245229 Primes that are the sum of 7 cubes and no fewer.

7, 47, 61, 103, 113, 211, 223, 229, 311, 337, 401, 419, 491, 787, 1021, 1453, 1489, 1697, 2039, 3659, 4703, 5279

Offset: 1

Author

Rafael F. Farias, Jul 13 2014

Keywords

• nonn
• less
• fini

Comments

Intersection of A018890 and A000040.

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

Examples

			a(1) = 7 = 1^3 + 1^3 + 1^3 + 1^3 + 1^3 + 1^3 + 1^3.
a(2) = 47 = 3^3 + 2^3 + 2^3 + 1^3 + 1^3 + 1^3 + 1^3.
a(3) = 61 = 3^3 + 2^3 + 2^3 + 2^3 + 2^3 + 1^3 + 1^3.
a(4) = 103 = 4^3 + 3^3 + 2^3 + 1^3 + 1^3 + 1^3 + 1^3.
		

Crossrefs

Cf. A000578, A018890, A000040.

Programs

Maple

for n from 1 to 10^4 do
  m:= floor(n^(1/3));
  if m^3 = n then M[n]:= 1
  else
    M[n]:= 1 + min(seq(M[n-j^3],j=1..m));
  fi
od:
select(n -> M[n]=7 and isprime(n), [$1..10^4]); # Robert Israel, Jul 14 2014