login

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

Floor(X/Y) where X = concatenation of (2n), (2n-1), ... down to n+1 and Y = concatenation of n, n-1, n-2, ... down to 1.
9

%I #11 Dec 02 2023 23:17:13

%S 2,2,2,2,2,185,18461,1842626,183987603,1837682236,1999303871,

%T 2000827643,2000777468,2000722020,2000673854,2000631711,2000594530,

%U 2000561482,2000531914,2000505305,2000481231,2000459347,2000439367

%N Floor(X/Y) where X = concatenation of (2n), (2n-1), ... down to n+1 and Y = concatenation of n, n-1, n-2, ... down to 1.

%e a(6) = floor(121110987/654321) = floor(185.094146451053840546153951959359) = 185.

%t f[n_] := (k = 1; x = y = "0"; While[k < n + 1, x = StringJoin[x, ToString[2n - k + 1]]; y = StringJoin[ToString[2k - 1], y]; k++ ]; Return[ Floor[10* ToExpression[x] / ToExpression[y]]] ); Table[ f[n], {n, 1, 25} ]

%t fd[st_,en_]:=FromDigits[Flatten[IntegerDigits/@Range[st,en,-1]]]; Table[ Floor[fd[2n,n+1]/fd[n,1]],{n,30}] (* _Harvey P. Dale_, Jul 04 2013 *)

%Y Cf. A067088.

%K easy,base,nonn

%O 1,1

%A _Amarnath Murthy_, Jan 07 2002

%E More terms from _Robert G. Wilson v_, Jan 09 2002

%E Offset corrected by _Sean A. Irvine_, Dec 02 2023