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A075013 Smallest k such that the decimal concatenation of k and k+1 is divisible by n. 0

%I #5 Apr 11 2020 12:39:49

%S 1,1,1,1,4,1,5,5,4,9,16,1,7,5,4,19,3,13,22,19,16,27,2,19,24,7,31,5,31,

%T 19,27,19,16,3,9,31,26,41,7,19,28,37,20,27,4,51,20,19,16,49,52,35,32,

%U 31,49,5,22,31,66,19,32,27,58,19,9,49,6,35,28,9,26,67,13,63,49,79,16

%N Smallest k such that the decimal concatenation of k and k+1 is divisible by n.

%e a(16) = 19 as 16 divides 1920.

%t With[{cnct=Table[FromDigits[Flatten[IntegerDigits/@{n,n+1}]],{n,100}]},Table[ Position[cnct,_?(Divisible[#,k]&),1,1],{k,100}]]//Flatten (* _Harvey P. Dale_, Apr 11 2020 *)

%o (PARI) for(n=1,100,k=1:while((k*(10^floor(log(k+1)/log(10)+1))+k+1)%n>0,k=k+1):print1(k","))

%Y Cf. A075114, A075115, A075116, A075117.

%K base,nonn

%O 1,5

%A _Amarnath Murthy_, Sep 01 2002

%E Corrected and extended by _Ralf Stephan_, Mar 23 2003

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Last modified March 28 13:35 EDT 2024. Contains 371254 sequences. (Running on oeis4.)