A147755 a(n) = the largest integer that, when represented in binary, occurs at least twice as a substring in the binary representation of n.

1, 0, 1, 1, 3, 0, 1, 2, 1, 1, 1, 3, 7, 0, 1, 2, 1, 2, 5, 2, 3, 1, 1, 2, 3, 3, 3, 7, 15, 0, 1, 2, 1, 4, 2, 2, 3, 2, 2, 10, 5, 2, 5, 3, 7, 1, 1, 2, 3, 2, 5, 6, 3, 3, 3, 3, 3, 7, 7, 15, 31, 0, 1, 2, 1, 4, 2, 2, 3, 4, 9, 2, 2, 4, 2, 3, 7, 2, 2, 2, 2, 10, 21, 5, 5, 2, 2, 5, 11, 3, 5, 7, 15, 1, 1, 2, 3, 4, 2, 6, 3, 2

Offset: 3

Author

Leroy Quet, Nov 11 2008

Keywords

• base
• nonn
• look

Comments

The substrings (each equal to the binary representation of a(n)) may overlap in the binary representation of n.

Examples

			21 in binary is 10101. 101 (5 in decimal) occurs twice in 10101: (101)01 and 10(101). Since no larger integer (when represented in binary) occurs more than once within 10101, then a(21) = 5.
		

Links

• Alois P. Heinz, Table of n, a(n) for n = 3..8190

Crossrefs

Cf. A147756, A242869.

Programs

Mathematica

Table[With[{d = IntegerDigits[n, 2]}, SelectFirst[Range[n, 0, -1], SequenceCount[d, IntegerDigits[#, 2], Overlaps -> True] >= 2 &]], {n, 3, 104}] (* Michael De Vlieger, Oct 30 2017 *)

Extensions

Extended by Ray Chandler, Nov 14 2008