This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A067090 #15 Dec 02 2023 23:17:08 %S A067090 2,3,5,7,8,981,114462,13082645,1471900839,1635537203,1799173568, %T A067090 1962809933,2126446298,2290082663,2453719028,2617355393,2780991758, %U A067090 2944628123,3108264488,3271900853,3435537218,3599173583,3762809948 %N A067090 Floor(X/Y) where X = concatenation of (2n), (2n-1), ... down to n+1 and Y = concatenation of 1,2,3,... up to n. %e A067090 a(4) = floor(8765/1234) = 7. %e A067090 a(6) = floor(121110987/123456) = floor(981.00527313374805598755832037325) = 981. %t A067090 f[n_] := (k = 1; x = y = "0"; While[k < n + 1, x = StringJoin[x, ToString[2n - k + 1]]; y = StringJoin[y, ToString[2k - 1]]; k++ ]; Return[ Floor[ ToExpression[x] / ToExpression[y]]] ); Table[ f[n], {n, 1, 25} ] %t A067090 Table[Floor[FromDigits[Flatten[IntegerDigits/@(Range[2n,n+1,-1])]]/FromDigits[Flatten[IntegerDigits/@(Range[n])]]],{n,25}] (* _Harvey P. Dale_, Jul 24 2011 *) %Y A067090 Cf. A067088, A067089. %K A067090 easy,base,nonn %O A067090 1,1 %A A067090 _Amarnath Murthy_, Jan 07 2002 %E A067090 More terms from _Robert G. Wilson v_, Jan 09 2002 %E A067090 Edited by _N. J. A. Sloane_ at the suggestion of _Andrew S. Plewe_, May 14 2007 %E A067090 Offset corrected by _Sean A. Irvine_, Dec 02 2023