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A068657
Successive left concatenation of floor(k/2) beginning with n until we reach 1.
2
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
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}]
Table[FromDigits[Flatten[IntegerDigits/@NestWhileList[Floor[#/2]&, n, #>1&]]], {n, 40}] (* Harvey P. Dale, Mar 09 2024 *)
CROSSREFS
Sequence in context: A256824 A176558 A243360 * A068671 A166668 A019423
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