OFFSET
1,1
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
433=1^3+3^3+4^3+5^3+6^3, 443=1^3+2^3+3^3+4^3+7^3, 541=1^3+2^3+4^3+5^3+7^3.
MAPLE
N:= 3000: # for all terms <= N
S:= {}:
for a from 1 while 5*a^3 < N do
for b from a+1 while a^3 + 4*b^3 < N do
for c from b+1 while a^3 + b^3 + 3*c^3 < N do
for d from c+1 while a^3 + b^3 + c^3 + 2*d^3 < N do
S:= S union select(isprime, {seq(a^3 + b^3 + c^3 + d^3 + e^3, e=d+1..floor((N-a^3-b^3-c^3-d^3)^(1/3)))})
od od od od:
sort(convert(S, list)); # Robert Israel, Jun 21 2019
MATHEMATICA
lst = {}; Do[Do[Do[Do[Do[p = a^3 + b^3 + c^3 + d^3 + e^3; If[PrimeQ[p], AppendTo[lst, p]], {e, d - 1, 1, -1}], {d, c - 1, 1, -1}], {c, b - 1, 1, -1}], {b, a - 1, 1, -1}], {a, 6, 20}]; Take[Union[lst], 80]
Module[{nn=15, upto}, upto=nn^3+9; Select[Union[Total/@Subsets[Range[nn]^3, {5}]], PrimeQ[#] && #<=upto&]] (* Harvey P. Dale, Aug 31 2023 *)
PROG
(PARI) cbrt(x)=if(x<0, x, x^(1/3));
upto(lim)=my(v=List(), tb, tc, td, te); for(a=6, lim^(1/3), for(b=4, min(a-1, cbrt(lim-a^2)), tb=a^3+b^3; for(c=3, min(b-1, cbrt(lim-tb)), tc=tb+c^3; for(d=2, min(c-1, cbrt(lim-tc)), td=tc+d^3; forstep(e=1+td%2, d-1, 2, te=td+e^3; if(te>lim, break); if(isprime(te), listput(v, te))))))); vecsort(Vec(v), , 8)
\\ Charles R Greathouse IV, Jul 17 2011
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladimir Joseph Stephan Orlovsky, Jul 16 2011
STATUS
approved