A120442 - OEIS

A120442

P-positions of John H. Conway's "Digit Deletions" game from "On Numbers and Games". Each number is the smallest positive integer that cannot be reduced to an earlier number in the sequence, by performing one of the following two operations: (1) changing one digit to a smaller digit (but not changing the leading digit to 0), or (2) deleting a 0 and all subsequent digits.

%I #10 Mar 06 2015 08:36:40

%S 1,11,20,32,43,54,65,76,87,98,111,120,132,143,154,165,176,187,198,201,

%T 210,222,233,244,255,266,277,288,299,300,312,321,334,345,353,367,378,

%U 386,402,413,424,431,440,456,468,475,489,497,503,514

%N P-positions of John H. Conway's "Digit Deletions" game from "On Numbers and Games". Each number is the smallest positive integer that cannot be reduced to an earlier number in the sequence, by performing one of the following two operations: (1) changing one digit to a smaller digit (but not changing the leading digit to 0), or (2) deleting a 0 and all subsequent digits.

%C The sequence is base-dependent, but notice that each number in a given base's sequence has a correspondent in all higher bases (the number with the same digit representation). The smallest n-digit number in the sequence is always a repunit.

%D John H. Conway, On Numbers and Games, 2nd Edition, pp. 190-192.

%e 201 is in the sequence because every number it may be reduced to (101, 2, 200) is not in the sequence: 101 and 2 both reduce to 1 and 200 reduces to 20.

%K base,easy,nonn

%O 1,2

%A Trevor Green (green(AT)math.usask.ca), Jul 18 2006