cp's OEIS Frontend

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.

Showing 1-3 of 3 results.

A087483 Row 0 of the order array of 3/2, i.e., row 0 of the transposable dispersion in A087465.

Original entry on oeis.org

1, 2, 4, 6, 9, 13, 17, 22, 28, 34, 41, 49, 57, 66, 76, 86, 97, 109, 121, 134, 148, 162, 177, 193, 209, 226, 244, 262, 281, 301, 321, 342, 364, 386, 409, 433, 457, 482, 508, 534, 561, 589, 617, 646, 676, 706, 737, 769, 801, 834, 868, 902, 937, 973, 1009, 1046, 1084
Offset: 0

Views

Author

Clark Kimberling, Sep 09 2003

Keywords

Comments

Also, column 0 of the transposable dispersion in A087468.

Crossrefs

Programs

Formula

a(n) = n + 1 - floor(n/3) + Sum_{i=1..n} floor(2i/3).
a(n) = 1 + floor((n+1)^2/3) = 1 + A000212(n+1).
a(n) = A192735(n+2) / (n+2). - Reinhard Zumkeller, Jul 08 2011
G.f.: -(x^4-x^3+x^2+1) / ((x-1)^3*(x^2+x+1)). - Colin Barker, Mar 31 2013

Extensions

Edited by Max Alekseyev, Dec 05 2013

A033291 A Connell-like sequence: take the first multiple of 1, the next 2 multiples of 2, the next 3 multiples of 3, etc.

Original entry on oeis.org

1, 2, 4, 6, 9, 12, 16, 20, 24, 28, 30, 35, 40, 45, 50, 54, 60, 66, 72, 78, 84, 91, 98, 105, 112, 119, 126, 133, 136, 144, 152, 160, 168, 176, 184, 192, 198, 207, 216, 225, 234, 243, 252, 261, 270, 280, 290, 300, 310, 320, 330, 340, 350, 360, 370, 374, 385, 396, 407, 418, 429, 440, 451, 462
Offset: 1

Views

Author

Keywords

Comments

Row sums are 0, 1, 6, 27, 88, 200, ... with g.f. -x*(1 + 4*x + 16*x^2 + 37*x^3 + 39*x^4 + 54*x^5 + 39*x^6 + 17*x^7 + 8*x^8 + x^9) / ( (1 + x + x^2)^3*(x-1)^5 ). - R. J. Mathar, Aug 10 2017

Examples

			Triangle begins
   1;
   2,  4;
   6,  9,  12;
  16, 20,  24,  28;
  30, 35,  40,  45,  50;
  54, 60,  66,  72,  78,  84;
  91, 98, 105, 112, 119, 126, 133; ...
		

Crossrefs

Cf. A192735 (left edge), A192736 (right edge).

Programs

  • Haskell
    a033291 n k = a033291_tabl !! (n-1) !! (k-1)
    a033291_row n = a033291_tabl !! (n-1)
    a033291_tabl = f 1 [1..] where
       f k xs = ys : f (k+1) (dropWhile (<= last ys) xs) where
         ys  = take k $ filter ((== 0) . (`mod` k)) xs
    a192735 n = head $ a033291_tabl !! (n-1)
    a192736 n = last $ a033291_tabl !! (n-1)
    -- Reinhard Zumkeller, Jan 18 2012, Jul 08 2011
    
  • Maple
    A033291 := proc(n,k)
        A192735(n)+(k-1)*n ;
    end proc:
    seq(seq(A033291(n,k),k=1..n),n=1..10) ; # R. J. Mathar, Aug 10 2017
  • Mathematica
    Flatten[ Table[ n*(Floor[ (n-1)^2/3] + k), {n, 1, 12}, {k, 1, n}]] (* Jean-François Alcover, Sep 30 2011 *)
  • PARI
    a(n)=my(q=(sqrtint(8*n-7)+1)\2); q*n-q*(q+1)\6*q \\ Charles R Greathouse IV, Jan 06 2016

Formula

a(n) = q(n)*n - q(n)*floor(q(n)*(q(n)+1)/6) with q(n) = ceiling((1/2)*(-1 + sqrt(1+8*(n)))).

Extensions

Corrected and formula added by Johannes W. Meijer, Oct 07 2010

A192736 Right edge of the triangle in A033291.

Original entry on oeis.org

1, 4, 12, 28, 50, 84, 133, 192, 270, 370, 484, 624, 793, 980, 1200, 1456, 1734, 2052, 2413, 2800, 3234, 3718, 4232, 4800, 5425, 6084, 6804, 7588, 8410, 9300, 10261, 11264, 12342, 13498, 14700, 15984, 17353, 18772, 20280, 21880, 23534, 25284, 27133, 29040
Offset: 1

Views

Author

Reinhard Zumkeller, Jul 08 2011

Keywords

Comments

a(n) = A007980(n-1) * n.

Crossrefs

Cf. A192735.

Programs

Formula

G.f.: x*(2*x^5+2*x^4+6*x^3+5*x^2+2*x+1) / ((x-1)^4*(x^2+x+1)^2). - Colin Barker, Mar 31 2013
Showing 1-3 of 3 results.