A259237 a(n) = least prime q such that q + prime(n) is a cube.

727, 5, 3, 1721, 53, 499, 47, 197, 41, 971, 1697, 179, 23, 173, 17, 11, 5, 3, 149, 929, 439, 137, 4013, 127, 2647, 1627, 113, 109, 107, 103, 89, 1597, 79, 373, 67, 2593, 59, 53, 3929, 43, 37, 331, 809, 23, 19, 17, 5, 2521, 773, 283, 3863, 761, 271, 5581, 743, 3833

Offset: 1

Author

Zak Seidov, Jun 22 2015

Keywords

• nonn
• look

Comments

Corresponding values of (a(n)+prime(n))^(1/3): 9,2,2,12,4,8,4,6,4,10,12,6,4,6,4,4,4,4,6,10,8,6,16,6,14,12,6,6,6,6,6.

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A157480, A259232.

Programs

Maple

f:= proc(n) local p,k;
  p:= ithprime(n);
  for k from ceil(p^(1/3)) do
    if isprime(k^3 - p) then return k^3 - p fi
  od
end proc:
map(f, [$1..100]); # Robert Israel, Oct 17 2023

Mathematica

Table[p=Prime[n];x=Ceiling[p^(1/3)];While[!PrimeQ[q=x^3-p],x++];q,{n,100}]

PARI

a(n) = {p = prime(n); k=2; while(!ispower(p+k,3), k = nextprime(k+1)); k;} \\ Michel Marcus, Jun 22 2015