|
|
A175210
|
|
a(n) = largest prime (or 1, if no such prime exists) that is < p(n) and whose binary representation occurs as a substring in the binary representation of p(n), where p(n) is the n-th prime.
|
|
2
|
|
|
1, 1, 2, 3, 5, 5, 2, 3, 11, 13, 7, 5, 5, 11, 23, 13, 29, 29, 3, 17, 2, 19, 41, 11, 3, 37, 19, 53, 13, 17, 31, 3, 17, 17, 37, 37, 29, 17, 83, 43, 89, 53, 47, 3, 17, 71, 83, 47, 113, 101, 41, 59, 113, 61, 2, 131, 67, 67, 17, 17, 17, 73, 19, 23, 19, 79, 41, 17, 173, 43, 97, 179, 47
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,3
|
|
COMMENTS
|
Only a(1) and a(2) = 1.
|
|
LINKS
|
|
|
EXAMPLE
|
29, the 10th prime, is 11101 in binary. The largest prime that is < 29 and whose binary representation occurs as a substring in this is 13 (1101 in binary), which occurs in binary 29 as follows: 1(1101). So a(10) = 13.
|
|
CROSSREFS
|
|
|
KEYWORD
|
base,nonn
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|