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.

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

Offset: 1

Author

Leroy Quet, Mar 05 2010

Keywords

• base
• nonn

Comments

Only a(1) and a(2) = 1.

Examples

			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.
		

Extensions

Extended by Ray Chandler, Mar 13 2010