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Smallest multiple of n with property that each digit is one less (mod 10) than the previous digit; or 0 if no such multiple exists.
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%I #9 Mar 29 2023 04:29:43

%S 0,1,2,3,4,5,6,7,8,9,10,21098,432,65,98,210,32,765,54,76,0,21,21098,

%T 109876543,432,0,109876,54,5432,87,210,321098,32,32109,432109876,210,

%U 432,2109,76,3210987,0,876543210987,210,43,432109876,765

%N Smallest multiple of n with property that each digit is one less (mod 10) than the previous digit; or 0 if no such multiple exists.

%H Sean A. Irvine, <a href="/A062399/b062399.txt">Table of n, a(n) for n = 0..1000</a>

%e a(13) = 65 = 13*5 has decreasing digits.

%t dtn[ L_ ] := Fold[ 10#1+#2&, 0, L ] a=Map[ dtn, Flatten[ Table[ Table[ Mod[ Range[ i, i-n+1, -1 ], 10 ], {i, 1, 9} ], {n, 1, 300} ], 1 ] ]; f[ n_ ] := Module[ {}, b=Select[ a, IntegerQ[ #/n ]& ]; If[ b=={}, 0, First[ b ] ] ] Table[ f[ n ], {n, 0, 63} ]

%K nonn,base,easy

%O 0,3

%A _Amarnath Murthy_, Jun 28 2001

%E More terms from _Erich Friedman_, Jun 30 2001