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A110404 Least multiple of n which is a repeated reverse concatenation of digits of n where n == 1, 3, 7 or 9 (mod 10). 1

%I #5 Dec 05 2013 19:57:02

%S 1,3,7,9,11,313131,7171717171717171,919191919191919191,121212,

%T 3232323232323232323232,727272,9292929292929292929292929292,

%U 131313131313131313131313131313,33,737373,939393,1414141414

%N Least multiple of n which is a repeated reverse concatenation of digits of n where n == 1, 3, 7 or 9 (mod 10).

%e For 13 the term is 313131 as 313131 = 13*24087.

%t f[n_] := Block[{k = 1, id = Reverse[ IntegerDigits[n]]}, While[fd = FromDigits[ Flatten[ Table[id, {k}]]]; Mod[fd, n] != 0, k++ ]; fd]; lst = Select[ Range[1, 41, 2], Mod[ #, 5] != 0 &]; f /@ lst (* _Robert G. Wilson v_ *)

%Y Cf. A110405.

%K base,easy,nonn

%O 1,2

%A _Amarnath Murthy_, Jul 30 2005

%E More terms from _Robert G. Wilson v_, Jul 30 2005

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Last modified April 17 05:47 EDT 2024. Contains 371756 sequences. (Running on oeis4.)