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.

A100236 Main diagonal of triangle A100235.

Original entry on oeis.org

1, 4, 26, 139, 726, 3774, 19601, 101784, 528526, 2744419, 14250626, 73997554, 384238401, 1995189564, 10360186226, 53796120699, 279340789726, 1450500069334, 7531841136401, 39109705751344, 203080369893126
Offset: 0

Views

Author

Paul D. Hanna, Nov 30 2004

Keywords

Crossrefs

Cf. A100233, A100235.
Equals A087130(n) - 1.

Programs

  • PARI
    a(n)=if(n==0,1,n*polcoeff(log((1-x)/(1-5*x-x^2)+x*O(x^n)),n))

Formula

a(n) = 5*a(n-1) + a(n-2) + 5 for n>1, with a(0)=1, a(1)=4. G.f.: Sum_{n>=1} a(n)*x^n/n = log((1-x)/(1-5*x-x^2)).

A100237 Secondary diagonal of triangle A100235 divided by row number: a(n) = A100235(n+1,n)/(n+1) for n >= 0.

Original entry on oeis.org

1, 4, 21, 109, 566, 2939, 15261, 79244, 411481, 2136649, 11094726, 57610279, 299146121, 1553340884, 8065850541, 41882593589, 217478818486, 1129276686019, 5863862248581, 30448587928924, 158106801893201, 820982597394929, 4263019788867846, 22136081541734159
Offset: 0

Views

Author

Paul D. Hanna, Nov 30 2004

Keywords

Comments

G.f. equals the ratio of the g.f.s of any two adjacent diagonals of triangle A100235.
a(n) is the number of compositions of n when there are 4 types of 1 and 5 types of other natural numbers. - Milan Janjic, Aug 13 2010

Links

Crossrefs

Cf. A100234, A100235, A100236.
First differences of A052918.
Cf. A052918.

Programs

  • Maple
    a[0]:=1: a[1]:=4: for n from 2 to 26 do a[n]:=5*a[n-1]+a[n-2] od: seq(a[n], n=0..21); # Zerinvary Lajos, Jul 26 2006
  • PARI
    a(n)=polcoeff((1-x)/(1-5*x-x^2)+x*O(x^n),n)
  • PARI
    Vec((1-x)/(1-5*x-x^2) + O(x^40)) \\ Colin Barker, Oct 13 2015

Formula

a(n) = 5*a(n-1) + a(n-2) for n>1, with a(0)=1, a(1)=4.
G.f.: (1-x)/(1-5*x-x^2).
Numerators in continued fraction [1, 4, 5, 5, 5, ...]. Continued fraction [1, 4, 5, 5, 5, ...] = 0.807417596433..., the inradius of a right triangle with legs 2 and 5. n-th convergent (n>0) to [1, 4, 5, 5, 5, ...] = A100237(n)/A052918(n), the first few being 1/1, 4/5, 21/26, 109/135, ... - Gary W. Adamson, Dec 21 2007
If p[1]=4, p[i]=5, (i>1), and if A is Hessenberg matrix of order n defined by: A[i,j]=p[j-i+1], (i<=j), A[i,j]=-1, (i=j+1), and A[i,j]=0 otherwise. Then, for n >= 1, a(n)=det A. - Milan Janjic, Apr 29 2010
a(n) = (2^(-1-n)*((5-sqrt(29))^n*(-3+sqrt(29)) + (3+sqrt(29))*(5+sqrt(29))^n))/sqrt(29). - Colin Barker, Oct 13 2015

A100234 G.f. A(x) satisfies: 6^n - 1 = Sum_{k=0..n} [x^k]A(x)^n and also satisfies: (6+z)^n - (1+z)^n + z^n = Sum_{k=0..n} [x^k](A(x)+z*x)^n for all z, where [x^k]A(x)^n denotes the coefficient of x^k in A(x)^n.

Original entry on oeis.org

1, 4, 5, -15, 20, 90, -695, 1785, 3895, -53985, 196255, 121635, -4907130, 23332140, -13181145, -470127465, 2866898820, -4455872910, -44776087145, 356263904235, -873534120380, -3988869806010, 44179467566755, -147200296896765, -293052319462105, 5409366658571715
Offset: 0

Views

Author

Paul D. Hanna, Nov 29 2004

Keywords

Comments

More generally, if g.f. A(x) satisfies: m^n-b^n = Sum_{k=0..n} [x^k]A(x)^n, then A(x) also satisfies: (m+z)^n - (b+z)^n + z^n = Sum_{k=0..n} [x^k](A(x)+z*x)^n for all z and A(x)=(1+(m-1)*x+sqrt(1+2*(m-2*b-1)*x+(m^2-2*m+4*b+1)*x^2))/2.

Examples

			From the table of powers of A(x) (A100235), we see that
6^n-1 = Sum of coefficients [x^0] through [x^n] in A(x)^n:
A^1=[1,4],5,-15,20,90,-695,1785,...
A^2=[1,8,26],10,-55,190,-245,-1690,...
A^3=[1,12,63,139],15,-120,635,-2130,...
A^4=[1,16,116,436,726],20,-210,1480,...
A^5=[1,20,185,965,2830,3774],25,-325,...
A^6=[1,24,270,1790,7335,17634,19601],30,...

Crossrefs

Cf. A100235, A100236, A100231.

Programs

  • PARI
    a(n)=if(n==0,1,(6^n-1-sum(k=0,n,polcoeff(sum(j=0,min(k,n-1),a(j)*x^j)^n+x*O(x^k),k)))/n)
  • PARI
    a(n)=if(n==0,1,if(n==1,4,if(n==2,5,-(3*(2*n-3)*a(n-1)+29*(n-3)*a(n-2))/n)))
  • PARI
    a(n)=polcoeff((1+5*x+sqrt(1+6*x+29*x^2+x^2*O(x^n)))/2,n)

Formula

a(n)=-(3*(2*n-3)*a(n-1)+29*(n-3)*a(n-2))/n for n>2, with a(0)=1, a(1)=4, a(2)=5. G.f.: A(x) = (1+5*x+sqrt(1+6*x+29*x^2))/2.
Showing 1-3 of 3 results.

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