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

0,3

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 It is known that there are infinitely many Coster numbers (result of David Kloet, Albert Hendriks and Arjen Stolk, unpublished).

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)

Example

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

Crossrefs

Cf. A036057.

Sequence in context: A293831 A118140 A108854 * A048037 A346657 A171492

Adjacent sequences: A106004 A106005 A106006 * A106008 A106009 A106010

Keyword

base,nonn

Author

Matthijs Coster, Dec 31 2006, Feb 02 2007

Status

approved