|
|
A107990
|
|
Primes representing areas of cube faces where the integer part of the cube's volume is also prime.
|
|
1
|
|
|
2, 3, 5, 43, 89, 113, 131, 163, 457, 467, 509, 541, 587, 739, 773, 887, 1109, 1123, 1201, 1307, 1319, 1409, 1613, 1741, 1747, 1787, 1979, 2063, 2069, 2459, 2467, 2671, 2689, 2741, 2789, 3187, 3203, 3539, 3547, 3557, 3643, 3823, 3917, 3989, 4021, 4441, 4447
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
COMMENTS
|
If the area of a single face of the cube is p, the volume is V=(sqrt(p))^3, and we look for cases where floor(V) and p are both prime.
|
|
LINKS
|
|
|
FORMULA
|
|
|
EXAMPLE
|
If the area of the cube is the prime p = 5, the side length is sqrt(5), the volume is 5^(3/2) = 11.18033..., and the truncated (floor) value of the volume is 11, a prime, which puts the prime p=5 to the sequence.
|
|
PROG
|
(PARI) g(n) = forprime(x=2, n, y=floor(sqrt(x)^3); if(isprime(y), print1(x, ", ")))
|
|
CROSSREFS
|
|
|
KEYWORD
|
easy,nonn
|
|
AUTHOR
|
|
|
EXTENSIONS
|
Offset set to 1, example expanded - R. J. Mathar, Sep 16 2009
|
|
STATUS
|
approved
|
|
|
|