# Greetings from The On-Line Encyclopedia of Integer Sequences! http://oeis.org/

Search: id:a282757
Showing 1-1 of 1

%I A282757 #8 Feb 23 2017 22:53:51
%S A282757 5,9,10,15,19,20,25,28,30,35,40,45,47,66,88,132,198,2006,2740,4012,
%T A282757 4419,13635,56357,338540,354164,419966,441972,685704,803678,1528803,
%U A282757 1844810,9127005,12305952,14315686,14650155,15828353,17838087,22618003,37826729,71644613
%N A282757 2*n analog to Keith numbers.
%C A282757 Like Keith numbers but starting from 2*n digits to reach n.
%C A282757 Consider the digits of 2*n. Take their sum and repeat the process deleting the first addend and adding the previous sum. The sequence lists the numbers that after some iterations reach a sum equal to themselves.
%e A282757 2*28 = 56 :
%e A282757 5 + 6 = 11;
%e A282757 6 + 11 = 17;
%e A282757 11 + 17 = 28.
%p A282757 with(numtheory): P:=proc(q, h,w) local a, b, k, n, t, v; v:=array(1..h);
%p A282757 for n from 1 to q do a:=w*n; b:=ilog10(a)+1; if b>1 then
%p A282757 for k from 1 to b do v[b-k+1]:=(a mod 10); a:=trunc(a/10); od; t:=b+1; v[t]:=add(v[k], k=1..b); while v[t]<n do t:=t+1; v[t]:=add(v[k], k=t-b..t-1); od;
%p A282757 if v[t]=n then print(n); fi; fi; od; end: P(10^6, 1000,2);
%t A282757 Select[Range[10^6], Function[n, Module[{d = IntegerDigits[2 n], s, k = 0}, s = Total@ d; While[s < n, AppendTo[d, s]; k++; s = 2 s - d[[k]]]; s == n]]] (* _Michael De Vlieger_, Feb 22 2017, after _T. D. Noe_ at A007629 *)
%Y A282757 Cf. A282758 - A282765.
%K A282757 nonn,base
%O A282757 1,1
%A A282757 _Paolo P. Lava_, Feb 22 2017

# Content is available under The OEIS End-User License Agreement: http://oeis.org/LICENSE