A078188 a(1) = 1; for n > 1 take the digits of a(n-1) one after the other and remove one occurrence of this digit from the digits of m = k*n (k > 0) if possible; a(n) is the smallest multiple m of n which has the least number of remaining digits (counted with multiplicity).

1, 2, 3, 4, 5, 6, 7, 8, 9, 90, 99, 96, 26, 28, 285, 528, 85, 18, 19, 20, 21, 22, 23, 24, 25, 52, 27, 28, 29, 90, 93, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71

Offset

1,2

Links

Table of n, a(n) for n=1..71.

Example

For n = 10 we have a(n-1) = a(9) = 9; removing 9 from 9*n = 9*10 = 90 results in one remaining digit (i.e. 0) and for every smaller multiple of 10 (i.e. 10, 20, ..., 80) there are two remaining digits, so a(10) = 90. For n = 20 we have a(n-1) = a(19) = 19; for 1*n = 1*20 = 20 no digit is removed and two digits remain and there is no multiple of 20 which has less than two remaining digits (for 100 twice the digit 0), so a(20) = 20.

Crossrefs

Sequence in context: A303171 A338831 A024664 * A240511 A345406 A198486

Adjacent sequences: A078185 A078186 A078187 * A078189 A078190 A078191

Keyword

base,nonn

Author

Amarnath Murthy, Nov 21 2002

Extensions

Edited, corrected and extended by Klaus Brockhaus, Dec 03 2002

Status

approved