login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A122478 Minimum number k>0 such that ((2n+1)^k - (2n-1)^k)/2 is prime. 2

%I

%S 3,13,3,3,5,3,17,3,163,3,3,109,3,13,19,5,3,3,1879,3,13,379,7,1531,7,5,

%T 337,5,3,61,19,3,23,3,11,16417,163,23,3,5,3,3,3,5

%N Minimum number k>0 such that ((2n+1)^k - (2n-1)^k)/2 is prime.

%C All a(n) are primes. Corresponding minimal primes of the form ((2n+1)^k - (2n-1)^k)/2 are {13, 609554401, 109, 193, 51001, 433, 44937854708156010721, 769, ...}.

%C a(46)-a(49) are 17, 5, 31, 3. a(51)-a(61) are 109, 5, 7, 89, 13, 3, 31, 53, 5, 3, 5. a(63)-a(69) are 3, 7, 19, 5, 167, 163, 293. a(71)-a(74) are 3, 3407, 3, 3. a(76)-a(77) are 3, 19.

%C a(45), a(50), a(62), a(70), a(75) are currently unknown.

%C a(45) > 30000. [From _Max Alekseyev_, May 18 2010]

%Y Cf. A028491, A121877.

%K hard,more,nonn

%O 1,1

%A _Alexander Adamchuk_, Sep 14 2006, Sep 17 2006, Oct 07 2006

%E a(36)=16417 from _Max Alekseyev_, May 11 2010

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.

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 23 11:52 EDT 2021. Contains 348212 sequences. (Running on oeis4.)