|
|
A232084
|
|
Least k such that prime(n) + 2^(k+L) - 2^L is a prime, where L is the length of binary representation of prime(n): L = A070939(A000040(n)). a(n) = -1 if no such k exists.
|
|
0
|
|
|
1, 1, 2, 2, 1, 2, 4, 4, 1, 2, 1, 2, 1, 2, 4, 2, 3, 4, 1, 2, 2, 1, 5, 4, 1, 2, 2, 4, 1, 6, 18, 20, 2, 4, 2, 3, 1, 4, 2, 2, 3, 6, 1, 12, 2, 1, 1, 96, 2, 4, 4, 2, 2, 1, 3, 3, 4, 6, 6, 4, 3, 6, 1, 4, 1, 2, 2, 1, 56, 2, 3, 8, 4, 4, 3, 4, 2, 4, 4, 3, 4, 4, 18, 20, 2, 8, 2, 2
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
2,3
|
|
COMMENTS
|
Least number of 1's that must be prepended to the binary representation of prime(n) such that the result is another prime.
Prime(n) is in A065047 if and only if a(n) = 1.
|
|
LINKS
|
|
|
EXAMPLE
|
a(6) = 1 because 13 in binary is 1101, and 29 (11101 in binary) is a prime.
a(7) = 2 because 17 in binary is 10001, and 113 (1110001 in binary) is a prime.
a(8) = 4 because 19 in binary is 10011, and 499 (111110011 in binary) is a prime.
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,base,less
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|