A105447 Positive integers whose representation as Roman Fibonacci numbers has exactly two symbols.

4, 6, 7, 9, 10, 11, 12, 14, 15, 16, 18, 19, 20, 22, 23, 24, 26, 29, 31, 32, 33, 35, 36, 37, 39, 42, 47, 50, 52, 53, 54, 56, 57, 58, 60, 63, 68, 76, 81, 84, 86, 87, 88, 90, 91, 92, 94, 97, 102, 110, 123, 131, 139, 141, 142, 143, 145, 146, 147, 149, 152, 157

Offset: 1

Author

Jonathan Vos Post, Apr 09 2005

Keywords

• base
• easy
• nonn

Examples

			In Roman Fibonacci number representation:
4 = "22", 6 = "33", 7 = "52", 9 = "81", 10 = "55", 11 = "83", 12 = "1A",
14 = "A1", 15 = "A2", 16 = "88", 18 = "3B", 19 = "2B", 20 = "1B", ...
143 = "1F", 145 = "F1", 146 = "F2", 147 = "F3", 149 = "F5", 152 = "F8".
		

Crossrefs

Cf. A000045, A006968, A105446, A105448-A105455.

Formula

a(n) is an element of A105447 iff A105446(n) = 2. a(n) is the sum or difference of two Fibonacci numbers A000045 and a(n) is not itself a Fibonacci number A000045.