A106007 Coster numbers: similar to Friedman numbers (A036057), but here the operations + - * / are allowed. All digits of a number have to be used exactly twice.

0, 1, 13, 14, 15, 18, 19, 24, 25, 26, 28, 29, 35, 36, 37, 39, 45, 46, 48, 49, 52, 55, 59, 64, 65, 66, 69, 73, 75, 78, 79, 81, 82, 85, 89, 91, 95, 99, 125, 126, 127, 128, 129, 134, 135, 136, 137, 138, 143, 144, 145, 146, 147, 148, 149, 152, 153, 154, 155, 156, 157, 158

Offset: 0

Author

Matthijs Coster, Dec 31 2006, Feb 02 2007

Keywords

• base
• nonn

Comments

These numbers were introduced in 2006 in the yearly number puzzle in the Dutch Journal "Pythagoras" (see http://www.pythagoras.nu). It is known that there are infinitely many Coster numbers (result of David Kloet, Albert Hendriks and Arjen Stolk, unpublished).

Examples

			36 is in the sequence since 3*6+3*6 = 36
		

Links

• Matthijs Coster, Feb 02 2007, Table of n, a(n) for n = 0..89
• Matthijs Coster, www.wiskundemeisjes.nl/20061030/coster-getallen/ (in Dutch)
• Matthijs Coster, www.matcos.nl/sequences
• Pythagoras, www.pythagoras.nu (in Dutch)

Crossrefs

Cf. A036057.