login
A247350
Numbers x such that 8*x^3 - 8*x^2 + 4*x + 1 is prime.
1
1, 2, 3, 4, 5, 7, 8, 12, 14, 15, 17, 22, 28, 33, 35, 39, 40, 45, 53, 57, 58, 59, 65, 70, 73, 74, 77, 80, 82, 83, 85, 93, 97, 99, 100, 102, 103, 104, 107, 115, 117, 118, 122, 128, 134, 139, 142, 143, 148, 152, 159, 164, 173, 178, 182, 184, 185, 188, 190, 195, 198
OFFSET
1,2
COMMENTS
Since 8*x^3 - 8*x^2 + 4*x + 1 = (2*x-1)^3 + (2x-1)^2 + (2x-1) + 2, the corresponding primes are of the form k^3 + k^2 + k + 2 and are in A088547.
LINKS
FORMULA
8*a(n)^3 - 8*a(n)^2 + 4*a(n) + 1 = A088547(n+1).
MATHEMATICA
Select[Range[1000], PrimeQ[1 + 4*# - 8*#^2 + 8*#^3] &]
PROG
(PARI) is(n)=isprime(8*n^3-8*n^2+4*n+1)
CROSSREFS
Cf. A088547 (primes of form k^3+k^2+k+2).
Sequence in context: A111795 A046098 A258085 * A057484 A091997 A124168
KEYWORD
nonn
AUTHOR
STATUS
approved