|
|
A074720
|
|
Least k such that floor(3^n/2^k) is prime.
|
|
1
|
|
|
2, 1, 4, 5, 6, 1, 11, 6, 7, 4, 5, 1, 9, 6, 8, 21, 8, 4, 25, 12, 20, 13, 30, 17, 6, 13, 10, 13, 19, 5, 12, 34, 33, 37, 16, 39, 35, 13, 38, 30, 28, 20, 53, 16, 60, 24, 40, 43, 34, 19, 23, 32, 63, 59, 19, 22, 27, 56, 86, 14, 29, 5, 53, 13, 15, 63, 19, 7, 88, 1, 87, 46, 22, 51, 25, 30
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
2,1
|
|
COMMENTS
|
|
|
LINKS
|
|
|
MAPLE
|
f:= proc(n) local t, k;
t:= 3^n;
for k from 1 do t:= t/2; if isprime(floor(t)) then return k fi od:
end proc:
|
|
MATHEMATICA
|
lk[n_]:=Module[{k=1, n3=3^n}, While[!PrimeQ[Floor[n3/2^k]], k++]; k]; Array[lk, 80, 2] (* Harvey P. Dale, Feb 24 2013 *)
|
|
PROG
|
(PARI) a(n)=if(n<0, 0, k=1; while(isprime(floor(3^n/2^k)) == 0, k++); k)
|
|
CROSSREFS
|
|
|
KEYWORD
|
easy,nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|