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 A068657 Successive left concatenation of floor(k/2) beginning with n until we reach 1. 1
 1, 21, 31, 421, 521, 631, 731, 8421, 9421, 10521, 11521, 12631, 13631, 14731, 15731, 168421, 178421, 189421, 199421, 2010521, 2110521, 2211521, 2311521, 2412631, 2512631, 2613631, 2713631, 2814731, 2914731, 3015731, 3115731, 32168421 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Every a(j) will divide some a(k), j < k. - Robert G. Wilson v, Mar 02 2002 LINKS EXAMPLE a(21) is constructed by starting with n, 21, then successively floor(21/2) = 10, floor(10/2) = 5, floor(5/2) = 2, floor(2/2) = 1, which is the end of the process of the halving. Now concatenate the results beginning with n: 21, 10, 5, 2, 1, which results in the number 2110521. MAPLE for m from 1 to 100 do a := m; n := m; while(n>1) do n := floor(n/2); if(n=1) then a := 10*a+1: else a := a*10^(ceil( log(n)/log(10)-0.000001) )+n:end if:end do:b[m] := a:end do:seq(b[i], i=1..100); MATHEMATICA f[n_] := Floor[n/2]; Table[ ToExpression[ StringJoin[ ToString /@ Drop[ FixedPointList[f, n], -2]]], {n, 1, 35}] CROSSREFS Sequence in context: A256824 A176558 A243360 * A068671 A166668 A019423 Adjacent sequences:  A068654 A068655 A068656 * A068658 A068659 A068660 KEYWORD base,easy,nonn AUTHOR Amarnath Murthy, Feb 28 2002 EXTENSIONS More terms from Sascha Kurz, Mar 26 2002 Corrected by Robert G. Wilson v, Mar 02 2002 STATUS approved

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Last modified May 14 04:27 EDT 2021. Contains 343872 sequences. (Running on oeis4.)