A138299 For number bases b (2 <= b <= 10) consider numbers that can be written as repdigits with at least two digits: the sequence gives products of such numbers also having this property (the number bases are not necessarily distinct).

9, 12, 15, 16, 18, 20, 21, 24, 27, 28, 30, 32, 33, 35, 36, 40, 42, 44, 45, 48, 50, 54, 55, 60, 63, 66, 70, 77, 80, 88, 91, 93, 99, 121, 124, 129, 156, 171, 172, 182, 215, 219, 228, 242, 255, 273, 285, 292, 312, 333, 341, 342, 364, 365, 400, 438, 444, 455, 468, 511, 546

Offset: 1

Author

Reinhard Zumkeller, Mar 14 2008

Keywords

• nonn
• base

Examples

			a(20) = 48 = 3*16:     66_7  =  11_2 *  22_7;
a(21) = 50 = 5*10:     55_9  =  11_4 *  22_4;
a(22) = 54 = 3*18:     66_8  =  11_2 *  33_5;
a(23) = 55 = 5*11:     55_10 =  11_4 *  11_10;
a(24) = 60 = 3*20:     66_9  =  11_2 *  22_9;
a(25) = 63 = 3*21: 111111_2  =  11_2 * 111_4;
a(26) = 66 = 3*22:     66_10 =  11_2 *  22_10;
a(27) = 70 = 5*14:     77_9  =  11_4 *  22_6;
a(28) = 77 = 7*11:     77_10 = 111_2 *  11_10;
a(29) = 80 = 4*20:   2222_3  =  11_3 *  22_9.
		

Links

• R. Zumkeller, Table of n, a(n) for n = 1..250
• R. Zumkeller, RepDigit Products
• Eric Weisstein's World of Mathematics, Repeating Decimal
• Eric Weisstein's World of Mathematics, Base