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.

A070937 Number of times maximal coefficient (A025591) appears in Product_{k<=n} (x^k + 1), i.e., number of times highest value appears in n-th row of A053632 or n-th column of A070936.

Original entry on oeis.org

1, 2, 4, 1, 5, 6, 4, 5, 1, 4, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1
Offset: 0

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Author

Henry Bottomley, May 12 2002

Keywords

Examples

			a(4)=5 since Product_{k<=4} (x^k + 1) = 1 + x + x^2 + 2x^3 + 2x^4 + 2x^5 + 2x^6 + 2x^7 + x^8 + x^9 + x^10 and 2 appears as a coefficient 5 times.
		

Formula

If n mod 4 = 0 or 3 then a(n) odd, otherwise a(n) even.
For n > 9: a(n) = A014695(n).
From Chai Wah Wu, Apr 10 2021: (Start)
a(n) = a(n-1) - a(n-2) + a(n-3) for n > 12.
G.f.: (2*x^12 - 2*x^11 + 6*x^10 - 4*x^9 + 6*x^8 - 2*x^7 - 2*x^6 + 2*x^5 - 6*x^4 + 2*x^3 - 3*x^2 - x - 1)/((x - 1)*(x^2 + 1)). (End)

A026836 Triangular array T read by rows: T(n,k) = number of partitions of n into distinct parts, the greatest being k, for k=1,2,...,n.

Original entry on oeis.org

1, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 0, 1, 1, 1, 0, 0, 1, 1, 1, 1, 0, 0, 0, 2, 1, 1, 1, 0, 0, 0, 1, 2, 1, 1, 1, 0, 0, 0, 1, 2, 2, 1, 1, 1, 0, 0, 0, 1, 2, 2, 2, 1, 1, 1, 0, 0, 0, 0, 2, 3, 2, 2, 1, 1, 1, 0, 0, 0, 0, 2, 3, 3, 2, 2, 1, 1, 1, 0, 0, 0, 0, 1, 3, 4, 3, 2, 2, 1, 1
Offset: 1

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Author

Keywords

Comments

Conjecture: A199918(n) = Sum_{k=1..n} (-1)^(n-k) T(n,k). - George Beck, Jan 13 2019

Examples

			Triangle begins:
[1]
[0, 1]
[0, 1, 1]
[0, 0, 1, 1]
[0, 0, 1, 1, 1]
[0, 0, 1, 1, 1, 1]
[0, 0, 0, 2, 1, 1, 1]
[0, 0, 0, 1, 2, 1, 1, 1]
[0, 0, 0, 1, 2, 2, 1, 1, 1]
[0, 0, 0, 1, 2, 2, 2, 1, 1, 1]
[0, 0, 0, 0, 2, 3, 2, 2, 1, 1, 1]
[0, 0, 0, 0, 2, 3, 3, 2, 2, 1, 1, 1]
[0, 0, 0, 0, 1, 3, 4, 3, 2, 2, 1, 1, 1]
[0, 0, 0, 0, 1, 3, 4, 4, 3, 2, 2, 1, 1, 1]
... - _N. J. A. Sloane_, Nov 09 2018
		

Crossrefs

If seen as a square array then transpose of A070936 and visible form of A053632. Central diagonal and those to the right of center are A000009 as are row sums.

Programs

  • Maple
    with(combinat);
    f2:=proc(n) local i,j,p,t0,t1,t2;
    t0:=Array(1..n,0);
    t1:=partition(n);
    p:=numbpart(n);
    for i from 1 to p do
    t2:=t1[i];
    if nops(convert(t2,set))=nops(t2) then
    # now have a partition t2 of n into distinct parts
    t0[t2[-1]]:=t0[t2[-1]]+1;
    od:
    [seq(t0[j],j=1..n)];
    end proc;
    for n from 1 to 12 do lprint(f2(n)); od: # N. J. A. Sloane, Nov 09 2018

Formula

T(n, k) = A070936(n-k, k-1) = A053632(k-1, n-k) = T(n-1, k-1)+T(n-2k+1, k-1). - Henry Bottomley, May 12 2002
T(n, k) = coefficient of x^n in x^k*Product_{i=1..k-1} (1+x^i). - Vladeta Jovovic, Aug 07 2003

A294250 Square array A(n,k), n >= 0, k >= 0, read by antidiagonals, where column k is the expansion of e.g.f.: exp(Product_{j=1..n} (1+x^j) - 1).

Original entry on oeis.org

1, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1, 1, 3, 1, 0, 1, 1, 3, 13, 1, 0, 1, 1, 3, 19, 49, 1, 0, 1, 1, 3, 19, 97, 261, 1, 0, 1, 1, 3, 19, 121, 681, 1531, 1, 0, 1, 1, 3, 19, 121, 921, 5971, 9073, 1, 0, 1, 1, 3, 19, 121, 1041, 8491, 50443, 63393, 1, 0, 1, 1, 3, 19, 121, 1041
Offset: 0

Views

Author

Seiichi Manyama, Oct 26 2017

Keywords

Examples

			Square array A(n,k) begins:
   1, 1,   1,   1,   1, ...
   0, 1,   1,   1,   1, ...
   0, 1,   3,   3,   3, ...
   0, 1,  13,  19,  19, ...
   0, 1,  49,  97, 121, ...
   0, 1, 261, 681, 921, ...
		

Crossrefs

Columns k=0..5 give A000007, A000012, A118589, A294251, A294252, A294253.
Rows n=0 gives A000012.
Main diagonal gives A293840.

Formula

B(j,k) is the coefficient of Product_{i=1..k} (1+x^i).
A(0,k) = 1 and A(n,k) = (n-1)! * Sum_{j=1..min(A000217(k),n)} j*B(j,k)*A(n-j,k)/(n-j)! for n > 0.
Showing 1-3 of 3 results.