OFFSET
1,3
COMMENTS
Except a(1)=0, a(n) are numbers k such that both k-x and y-k are perfect cubes, where x and y are two nearest to k cubes: x < k <= y.
LINKS
Donovan Johnson, Table of n, a(n) for n = 1..1000
EXAMPLE
152 is in the sequence because the following are cubes: 152-125=27 and 216-152=64, where 125 and 216 are the nearest to 152 cubes.
PROG
(C)
#include <stdio.h>
#include <gmp.h> // gcc -O3 A234348.c -lgmp
int main() {
long long in=0;
mpz_t n, r, i;
mpz_init(r);
mpz_init(i);
mpz_init_set_ui(n, in);
while (in < (1ULL<<32)) {
if (mpz_root(r, n, 3) && in) mpz_sub_ui(r, r, 1);
mpz_mul(i, r, r);
mpz_mul(i, i, r);
mpz_sub(i, n, i);
if (mpz_root(i, i, 3)) {
mpz_add_ui(r, r, 1);
mpz_mul(i, r, r);
mpz_mul(i, i, r);
mpz_sub(i, i, n);
if (mpz_root(i, i, 3)) printf("%llu, ", in);
}
mpz_add_ui(n, n, 1);
if ((++in&0xfffff)==0) printf(".");
}
return 0;
}
CROSSREFS
KEYWORD
nonn
AUTHOR
Alex Ratushnyak, Dec 24 2013
STATUS
approved