This site is supported by donations to The OEIS Foundation. Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A128026 Numbers n such that (10^n - 3^n)/7 is prime. 29
 2, 3, 5, 37, 599, 38393, 51431 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS All terms are primes. No other terms < 100000. LINKS MATHEMATICA k=7; Select[ Prime[ Range[1, 200] ], PrimeQ[ ((k+3)^# - 3^#)/k ]& ] PROG (PARI) forprime(p=2, 1e4, if(ispseudoprime((10^p-3^p)/7), print1(p", "))) \\ Charles R Greathouse IV, Jun 05 2011 CROSSREFS Cf. A028491 = numbers n such that (3^n - 1)/2 is prime. Cf. A057468 = numbers n such that 3^n - 2^n is prime. Cf. A059801 = numbers n such that 4^n - 3^n is prime. Cf. A121877 = numbers n such that (5^n - 3^n)/2 is a prime. Cf. A128024, A128025, A128027, A128028, A128029, A128030, A128031, A128032. Sequence in context: A271387 A089213 A029499 * A041443 A057775 A215321 Adjacent sequences:  A128023 A128024 A128025 * A128027 A128028 A128029 KEYWORD hard,nonn AUTHOR Alexander Adamchuk, Feb 11 2007 EXTENSIONS a(6)-a(7) from Robert Price, Jun 04 2011 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified May 19 07:05 EDT 2019. Contains 323386 sequences. (Running on oeis4.)