|
%I #13 Apr 06 2020 13:57:19
%S 2,11,50,52,69,101,250,252,500,502,685,750,752,1001,1250,3136,3752,
%T 5000,5002,6250,8752,10001,18752,31250,46329,50000,50002,68752,81250,
%U 84168,100001,218752,281250,297540,500000,500002,718752,749500,781250,1000001,1638694,2914261
%N Numbers k that are a substring of k*(k-1).
%C Any number of the forms 10^m+1, 5*10^m and 5*10^m+2 (m>0) are part of the sequence.
%H Paolo P. Lava, <a href="/A316263/b316263.txt">Table of n, a(n) for n = 1..93</a>
%e 69 * 68 = 4692;
%e 8752 * 8751 = 76588752.
%p P:=proc(q) local k,n; for n from 1 to q do
%p for k from 1 to ilog10(n*(n-1))-ilog10(n)+1 do
%p if n=trunc(n*(n-1)/10^(k-1)) mod 10^(ilog10(n)+1) then print(n);
%p break; fi; od; od; end: P(10^8);
%t Select[Range[3*10^6],SequenceCount[IntegerDigits[#(#-1)],IntegerDigits[ #]]>0&] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Apr 06 2020 *)
%Y Cf. A305670.
%K nonn,base,easy
%O 1,1
%A _Paolo P. Lava_, Jun 28 2018
|
