|
|
A302387
|
|
a(n) is least number k >= 3 such that (k^(2^n) + (k-2)^(2^n))/2 is prime.
|
|
0
|
|
|
3, 3, 3, 5, 3, 3, 3, 179, 169, 935, 663, 8723, 1481, 2035, 10199, 18203, 36395
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
0,1
|
|
LINKS
|
|
|
EXAMPLE
|
a(10)=663 corresponds to the prime (663^1024 + 661^1024)/2.
|
|
MATHEMATICA
|
lst = {}; For[n=0, n<=14, n++, k=3; While[! PrimeQ[(k^(2^n) + (k-2)^(2^n))/2], k++]; AppendTo[lst, k]]; lst (* Robert Price, Apr 29 2018 *)
|
|
PROG
|
(PARI) for(n=0, 20, forstep(k=3, +oo, 2, if(ispseudoprime((k^(2^n)+(k-2)^(2^n))/2), print1(k, ", "); break())))
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,hard,more
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|