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Numbers n which divide the right concatenation of the first n even numbers.
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%I #12 Jan 25 2024 20:19:12

%S 1,2,3,4,5,6,8,9,10,12,14,15,18,20,24,25,30,35,36,39,40,45,50,60,72,

%T 75,80,90,100,120,125,144,150,180,200,204,225,240,250,300,360,375,400,

%U 450,500,507,540,585,600,624,625,675,702,720,750,780,800,804,864,900

%N Numbers n which divide the right concatenation of the first n even numbers.

%e The right concatenation of the first six even numbers is 24681012 and 6 divides this number. So 6 is a member of the sequence.

%p a := proc(n): if n=1 then RETURN(2) fi: 2*n+a(n-1)*10^(ceil(log[10](2*n+.01))) end: for n from 1 to 1000 do if a(n) mod n = 0 then printf(`%d,`,n) fi; od:

%t concat[n_]:=FromDigits[Flatten[IntegerDigits/@Range[2,2n,2]]]; Select[ Range[700],Divisible[concat[#],#]&] (* _Harvey P. Dale_, Nov 02 2011 *)

%Y Cf. A029455.

%K base,easy,nonn

%O 1,2

%A _Amarnath Murthy_, Feb 19 2002

%E Edited and extended by _James A. Sellers_, Feb 20, 2002

%E Offset corrected by _Sean A. Irvine_, Jan 25 2024