OFFSET
1,1
COMMENTS
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, ...}.
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.
a(45), a(50), a(62), a(70), a(75) are currently unknown.
a(45) > 30000. - Max Alekseyev, May 18 2010
MATHEMATICA
s={}; Do[k=1; Until[PrimeQ[((2n+1)^k-(2n-1)^k)/2], k++]; AppendTo[s, k] , {n, 35}]; s (* James C. McMahon, Oct 27 2024 *)
CROSSREFS
KEYWORD
hard,more,nonn,changed
AUTHOR
Alexander Adamchuk, Sep 14 2006, Sep 17 2006, Oct 07 2006
EXTENSIONS
a(36)=16417 from Max Alekseyev, May 11 2010
STATUS
approved