A164794 a(n) is the smallest number whose English name has the letter "f" in the n-th position, or -1 if no such number exists.

4, -1, 15, -1, -1, 44, 24, 74, -1, -1, 104, 404, 115, 415, 315, 144, 124, 174, 324, 374, 3074, 1104, 1404, 1115, 1415, 1315, 1144, 1124, 1174, 1324, 1374, 3324, 3374, 11374, 13324, 13374, 17374, 23324, 23374, 73374, 101374, 103324, 103374, 111374, 113324

Offset: 1

Author

Claudio Meller, Aug 26 2009

Keywords

• word
• sign

Examples

			a(1)=4 ("Four"), a(3)=15 ("fiFteen"), a(11)=104 ("onehundredFour").
		

Crossrefs

Cf. A164789 ("o"), A164790 ("e"), A164791 ("n"), A164792 ("t").

Cf. A164793 ("i"), A164795 ("h"), A164796 ("r"), A164797 ("u").

Extensions

a(21) and beyond from Michael S. Branicky, Feb 02 2021