A074852 Composite n such that n and n+2 are prime powers.

9, 25, 27, 81, 125, 6561, 24389, 59049, 161051, 357911, 571787, 1442897, 4782969, 5177717, 14348907, 18191447, 30080231, 73560059, 80062991, 118370771, 127263527, 131872229, 318611987, 344472101, 440711081, 461889917, 590589719

Offset

1,1

Links

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Prog

(PARI) list(lim)=my(v=List(), t); lim+=.5; for(e=2, log(lim)\log(3), forprime(p=3, lim^(1/e), ispower(t=p^e+2, , &t); if(isprime(t), listput(v, p^e)))); vecsort(Vec(v))
\\ Charles R Greathouse IV, Apr 30 2012
(PARI) list(lim)=my(v=List()); if(lim>=25, listput(v, 25)); lim+=.5; for(e=2, log(lim)\log(3), forprime(p=3, lim^(1/e), if(isprime(p^e+2), listput(v, p^e)))); vecsort(Vec(v))
/* This second program assumes A076427(2) = 1 but is about a hundred times faster. I proved that it is correct up to 10^20 without this assumption. */
\\ Charles R Greathouse IV, Apr 30 2012

Crossrefs

Cf. A006549, A053702.

Sequence in context: A108989 A352492 A068583 * A322177 A346068 A352519

Adjacent sequences: A074849 A074850 A074851 * A074853 A074854 A074855

Keyword

nonn

Author

Benoit Cloitre, Sep 10 2002

Extensions

More terms from Sascha Kurz, Jan 30 2003

Status

approved