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.

Previous Showing 11-16 of 16 results.

A338223 G.f.: (1 / theta_4(x) - 1)^2 / 4, where theta_4() is the Jacobi theta function.

Original entry on oeis.org

1, 4, 12, 30, 68, 144, 289, 556, 1034, 1868, 3292, 5678, 9608, 15984, 26188, 42314, 67509, 106460, 166090, 256552, 392628, 595696, 896484, 1338894, 1985298, 2923840, 4278448, 6222518, 8997544, 12938368, 18507297, 26340040, 37307326, 52597320, 73825504, 103180702
Offset: 2

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Author

Ilya Gutkovskiy, Jan 30 2021

Keywords

Crossrefs

Programs

  • Maple
    g:= proc(n, i) option remember; `if`(n=0, 1/2, `if`(i=1, 0,
          g(n, i-1))+add(2*g(n-i*j, i-1), j=`if`(i=1, n, 1)..n/i))
        end:
    b:= proc(n, k) option remember; `if`(k=0, 1, `if`(k=1, `if`(n=0, 0,
          g(n$2)), (q-> add(b(j, q)*b(n-j, k-q), j=0..n))(iquo(k, 2))))
        end:
    a:= n-> b(n, 2):
    seq(a(n), n=2..37);  # Alois P. Heinz, Feb 10 2021
  • Mathematica
    nmax = 37; CoefficientList[Series[(1/EllipticTheta[4, 0, x] - 1)^2/4, {x, 0, nmax}], x] // Drop[#, 2] &
    nmax = 37; CoefficientList[Series[(1/4) (-1 + Product[(1 + x^k)/(1 - x^k), {k, 1, nmax}])^2, {x, 0, nmax}], x] // Drop[#, 2] &
    A015128[n_] := Sum[PartitionsP[k] PartitionsQ[n - k], {k, 0, n}]; a[n_] := (1/4) Sum[A015128[k] A015128[n - k], {k, 1, n - 1}]; Table[a[n], {n, 2, 37}]

Formula

G.f.: (1/4) * (-1 + Product_{k>=1} (1 + x^k) / (1 - x^k))^2.
a(n) = Sum_{k=0..n} A014968(k) * A014968(n-k).
a(n) = (1/4) * Sum_{k=1..n-1} A015128(k) * A015128(n-k).
a(n) = (A001934(n) - 2 * A015128(n)) / 4 for n > 0.

A023626 Self-convolution of (1, p(1), p(2), ...).

Original entry on oeis.org

1, 4, 10, 22, 43, 80, 137, 222, 343, 508, 737, 1030, 1411, 1888, 2477, 3198, 4059, 5096, 6297, 7702, 9327, 11176, 13301, 15682, 18355, 21344, 24673, 28358, 32411, 36896, 41769, 47082, 52883, 59148, 65937, 73298, 81251, 89776, 98957
Offset: 1

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Author

Keywords

Comments

p(1),p(2),p(3)... are the prime numbers (A000040). The analogous sequence for the partition numbers is A048574.

Examples

			G.f. = x + 4*x^2 + 10*x^3 + 22*x^4 + 43*x^5 + 80*x^6 + 137*x^7 + ...
		

Crossrefs

Programs

  • Haskell
    a023626 n = a023626_list !! (n-2)
    a023626_list = f a000040_list [1] where
       f (p:ps) rs = (sum $ zipWith (*) rs a008578_list) : f ps (p : rs)
    -- Reinhard Zumkeller, Nov 09 2015
  • Mathematica
    z = 100; p = Join[{1}, Prime[Range[z]]];
    a[n_] := Sum[p[[i]] p[[n - i + 1]], {i, 1, n}];
    Table[a[n], {n, 1, z}]  (* Clark Kimberling, Dec 01 2016 *)
    a[ n_] := If[ n < 1, 0, SeriesCoefficient[ (1 + O[x]^n + Sum[ Prime[k] x^k, {k, n - 1}])^2, {x, 0, n - 1}]]; (* Michael Somos, Dec 01 2016 *)
    Table[With[{c=Join[{1},Prime[Range[n]]]},ListConvolve[c,c]],{n,0,40}]// Flatten (* Harvey P. Dale, Oct 19 2018 *)

Formula

G.f: x*(1+b(x))^2 = (c(x)^2)/x, where b(x) and c(x) are respectively the g.f. of A000040 and A008578. - Mario C. Enriquez, Dec 10 2016

A304789 Number T(n,k) of partitions of 2n whose Ferrers-Young diagram allows exactly k different domino tilings; triangle T(n,k), n>=0, 0<=k<=A304790(n), read by rows.

Original entry on oeis.org

0, 1, 0, 2, 0, 4, 1, 1, 6, 2, 2, 2, 10, 3, 4, 1, 2, 6, 14, 4, 6, 4, 4, 0, 2, 2, 12, 22, 5, 8, 7, 6, 2, 4, 4, 0, 0, 4, 1, 2, 25, 30, 6, 10, 12, 10, 4, 6, 6, 0, 2, 8, 2, 4, 0, 2, 0, 0, 4, 2, 0, 2, 46, 44, 7, 12, 17, 14, 8, 8, 8, 0, 4, 12, 5, 6, 0, 8, 2, 0, 8, 4, 0, 4, 0, 0, 0, 2, 2, 0, 0, 4, 1, 2, 0, 0, 2, 0, 1
Offset: 0

Views

Author

Alois P. Heinz, May 18 2018

Keywords

Examples

			T(2,2) = 1: 22.
T(3,0) = 1: 321.
T(3,1) = 6: 111111, 21111, 3111, 411, 51, 6.
T(3,2) = 2: 2211, 42.
T(3,3) = 2: 222, 33.
T(8,36) = 1: 4444.
Triangle T(n,k) begins:
   0,  1;
   0,  2;
   0,  4, 1;
   1,  6, 2,  2;
   2, 10, 3,  4,  1,  2;
   6, 14, 4,  6,  4,  4, 0, 2, 2;
  12, 22, 5,  8,  7,  6, 2, 4, 4, 0, 0, 4, 1, 2;
  25, 30, 6, 10, 12, 10, 4, 6, 6, 0, 2, 8, 2, 4, 0, 2, 0, 0, 4, 2, 0, 2;
		

Crossrefs

Columns k=0-1 give: A304710, A139582(n) = 2*A000041(n) for n>0.
Row sums give A058696(n) or A000041(2n).

Programs

  • Maple
    h:= proc(l, f) option remember; local k; if min(l[])>0 then
         `if`(nops(f)=0, 1, h(map(u-> u-1, l[1..f[1]]), subsop(1=[][], f)))
        else for k from nops(l) while l[k]>0 by -1 do od;
            `if`(nops(f)>0 and f[1]>=k, h(subsop(k=2, l), f), 0)+
            `if`(k>1 and l[k-1]=0, h(subsop(k=1, k-1=1, l), f), 0)
          fi
        end:
    g:= l-> x^`if`(add(`if`(l[i]::odd, (-1)^i, 0), i=1..nops(l))=0,
              `if`(l=[], 1, h([0$l[1]], subsop(1=[][], l))), 0):
    b:= (n, i, l)-> `if`(n=0 or i=1, g([l[], 1$n]), b(n, i-1, l)
                      +b(n-i, min(n-i, i), [l[], i])):
    T:= n-> (p-> seq(coeff(p, x, i), i=0..degree(p)))(b(2*n$2, [])):
    seq(T(n), n=0..11);

Formula

Sum_{k>0} k * T(n,k) = A304662(n).
T(n,A304790(n)) = 1 for n in { A001105 }.
Sum_{k>=0} T(n,k) = A058696(n) = A000041(2n).
Sum_{k>=1} T(n,k) = A000712(n).
Sum_{k>=2} T(n,k) = A048574(n) = A052837(n).

A341236 Expansion of (-1 + Product_{k>=1} 1 / (1 - x^k))^10.

Original entry on oeis.org

1, 20, 210, 1550, 9055, 44624, 192945, 751480, 2686155, 8934560, 27946335, 82884860, 234636435, 637416140, 1669127130, 4228739712, 10398140075, 24882425770, 58080468790, 132508486900, 296005537183, 648445364080, 1394961003490, 2950516502980, 6142674032345, 12599932782780
Offset: 10

Views

Author

Ilya Gutkovskiy, Feb 07 2021

Keywords

Crossrefs

Programs

  • Maple
    b:= proc(n, k) option remember; `if`(k<2, `if`(n=0, 1-k, combinat[
          numbpart](n)), (q-> add(b(j, q)*b(n-j, k-q), j=0..n))(iquo(k, 2)))
        end:
    a:= n-> b(n, 10):
    seq(a(n), n=10..35);  # Alois P. Heinz, Feb 07 2021
  • Mathematica
    nmax = 35; CoefficientList[Series[(-1 + Product[1/(1 - x^k), {k, 1, nmax}])^10, {x, 0, nmax}], x] // Drop[#, 10] &

A052837 Number of partitions of 2n whose Ferrers-Young diagram allows more than one different domino tiling.

Original entry on oeis.org

0, 0, 1, 4, 10, 22, 43, 80, 141, 240, 397, 640, 1011, 1568, 2395, 3604, 5360, 7876, 11460, 16510, 23588, 33418, 47006, 65640, 91085, 125596, 172215, 234820, 318579, 430060, 577920, 773130, 1030007, 1366644, 1806445, 2378892, 3121835, 4082796, 5322360, 6916360
Offset: 0

Views

Author

encyclopedia(AT)pommard.inria.fr, Jan 25 2000

Keywords

Comments

The original name was: A simple grammar.

Crossrefs

Essentially the same as A048574.

Programs

  • Maple
    spec := [S,{C=Sequence(Z,1 <= card),B=Set(C,1 <= card),S=Prod(B,B)},unlabeled]: seq(combstruct[count](spec,size=n), n=0..20);
    # second Maple program:
    a:= n-> (p-> add(p(j)*p(n-j), j=1..n-1))(combinat[numbpart]):
    seq(a(n), n=0..40);  # Alois P. Heinz, May 26 2018
  • Mathematica
    a[n_] := If[n <= 1, 0, With[{pp = Array[PartitionsP, n-1]},
       First[ListConvolve[pp, pp]]]];
    Table[a[n], {n, 0, 40}] (* Jean-François Alcover, Jan 30 2025 *)

Formula

G.f.: (exp(Sum_{j>=1} -x^j/((x^j-1)*j) )-1)^2.
a(n) = Sum_{k>=2} A304789(n,k). - Alois P. Heinz, May 26 2018

Extensions

More terms from Franklin T. Adams-Watters, Feb 08 2006
New name from Alois P. Heinz, May 26 2018

A132993 Triangle t(n,m) = P(n-m+1) * P(m+1) read by rows, 0<=m<=n, where P=A000041 are the partition numbers.

Original entry on oeis.org

1, 2, 2, 3, 4, 3, 5, 6, 6, 5, 7, 10, 9, 10, 7, 11, 14, 15, 15, 14, 11, 15, 22, 21, 25, 21, 22, 15, 22, 30, 33, 35, 35, 33, 30, 22, 30, 44, 45, 55, 49, 55, 45, 44, 30, 42, 60, 66, 75, 77, 77, 75, 66, 60, 42, 56, 84, 90, 110, 105, 121, 105, 110, 90, 84, 56
Offset: 0

Views

Author

Roger L. Bagula and Gary W. Adamson, Aug 27 2008

Keywords

Examples

			1;
2, 2;
3, 4, 3;
5, 6, 6, 5;
7, 10, 9, 10, 7;
11, 14, 15, 15, 14, 11;
15, 22, 21, 25, 21, 22, 15;
22, 30, 33, 35, 35, 33, 30, 22;
30, 44, 45, 55, 49, 55, 45, 44, 30;
42, 60, 66, 75, 77, 77, 75, 66, 60, 42;
56, 84, 90, 110, 105, 121, 105, 110, 90, 84, 56;
		

Crossrefs

Cf. A000041, A048574 (row sums).

Programs

  • Maple
    A132993 := proc(n,m)
            combinat[numbpart](n-m+1)*combinat[numbpart](m+1) ;
    end proc:
    seq(seq(A132993(n,k),k=0..n),n=0..12) ; # R. J. Mathar, Nov 11 2011
  • Mathematica
    << DiscreteMath`Combinatorica`; << DiscreteMath`IntegerPartitions`; Clear[t, n, m]; t[n_, m_] = PartitionsP[n - m + 1]*PartitionsP[m + 1]; Table[Table[t[n, m], {m, 0, n}], {n, 0, 10}]; Flatten[%]
Previous Showing 11-16 of 16 results.