This site is supported by donations to The OEIS Foundation. Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A128067 Numbers k such that (3^k + 7^k)/10 is prime. 9
 3, 13, 31, 313, 3709, 7933, 14797, 30689, 38333 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS All terms are primes. a(10) > 10^5. - Robert Price, Oct 03 2012 LINKS MATHEMATICA k=7; Do[ p=Prime[n]; f=(3^p+k^p)/(k+3); If[ PrimeQ[f], Print[p]], {n, 1, 100} ] PROG (PARI) is(n)=isprime((3^n+7^n)/10) \\ Charles R Greathouse IV, Feb 17 2017 CROSSREFS Cf. A007658 = numbers n such that (3^n + 1)/4 is prime. Cf. A057469 = numbers n such that (3^n + 2^n)/5 is prime. Cf. A122853 = numbers n such that (3^n + 5^n)/8 is prime. Cf. A128066, A128068, A128069, A128070, A128071, A128072, A128073, A128074, A128075. 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, A128026, A128027, A128028, A128029, A128030, A128031, A128032. Sequence in context: A159047 A219971 A073337 * A052493 A279068 A247216 Adjacent sequences:  A128064 A128065 A128066 * A128068 A128069 A128070 KEYWORD hard,more,nonn AUTHOR Alexander Adamchuk, Feb 14 2007 EXTENSIONS More terms from Ryan Propper, Apr 02 2007 a(7)-a(9) from Robert Price, Oct 03 2012 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 23 04:59 EDT 2019. Contains 323508 sequences. (Running on oeis4.)