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.

A165937 G.f.: A(x) = exp( Sum_{n>=1} A002203(n^2)*x^n/n ).

Original entry on oeis.org

1, 2, 19, 964, 334965, 742714950, 10042408885191, 814556580116590856, 393147641272746246076745, 1123539400297807898234860367690, 18948227277012085227250633551784337179, 1881331163508674280605070386666674939623268684
Offset: 0

Views

Author

Paul D. Hanna, Oct 18 2009

Keywords

Comments

A002203 equals the logarithmic derivative of the Pell numbers (A000129).
Note that A002203(n^2) = (1+sqrt(2))^(n^2) + (1-sqrt(2))^(n^2).
Given g.f. A(x), (1-x)^(1/4) * A(x)^(1/8) is an integer series.

Examples

			G.f.: A(x) = 1 + 2*x + 19*x^2 + 964*x^3 + 334965*x^4 + 742714950*x^5 +...
log(A(x)) = 2*x + 34*x^2/2 + 2786*x^3/3 + 1331714*x^4/4 + 3710155682*x^5/5 + 60245508192802*x^6/6 + 5701755387019728962*x^7/7 +...+ A002203(n^2)*x^n/n +...
		

Crossrefs

Programs

  • PARI
    {a(n)=if(n==0,1,polcoeff(exp(sum(m=1,n,polcoeff(2*(1-x)/(1-2*x-x^2+x*O(x^(m^2))),m^2)*x^m/m)+x*O(x^(n^2))),n))}

Formula

Logarithmic derivative equals A165938.
Self-convolution of A166879.

A204327 a(n) = Pell(n^2).

Original entry on oeis.org

1, 12, 985, 470832, 1311738121, 21300003689580, 2015874949414289041, 1111984844349868137938112, 3575077977948634627394046618865, 66992092050551637663438906713182313772, 7316660981177400006023755031791634132229378601
Offset: 1

Views

Author

Paul D. Hanna, Jan 14 2012

Keywords

Examples

			G.f.: A(x) = x + 12*x^2 + 985*x^3 + 470832*x^4 + 1311738121*x^5 +...
		

Crossrefs

Programs

  • PARI
    {Pell(n)=polcoeff(x/(1-2*x-x^2+x*O(x^n)), n)}
    {a(n)=Pell(n^2)}

Formula

a(n) = ( (1+sqrt(2))^(n^2) - (1-sqrt(2))^(n^2) ) / (2*sqrt(2)).

A166879 G.f.: A(x) = exp( Sum_{n>=1} A002203(n^2)/2*x^n/n ).

Original entry on oeis.org

1, 1, 9, 473, 166969, 371186249, 5020831641761, 407273265807001089, 196573413317730320842177, 561769503571822735164882969633, 9474113076734769687535254457293566857, 940665572280219007549184269220597591870817337
Offset: 0

Views

Author

Paul D. Hanna, Oct 22 2009

Keywords

Comments

A002203 equals the logarithmic derivative of the Pell numbers (A000129).
Note that A002203(n^2) = (1+sqrt(2))^(n^2) + (1-sqrt(2))^(n^2).

Examples

			G.f.: A(x) = 1 + x + 9*x^2 + 473*x^3 + 166969*x^4 + 371186249*x^5 +...
log(A(x)) = x + 17*x^2/2 + 1393*x^3/3 + 665857*x^4/4 + 1855077841*x^5/5 + 30122754096401*x^6/6 + 2850877693509864481*x^7/7 +...+ A002203(n^2)/2*x^n/n +...
		

Crossrefs

Programs

  • PARI
    {a(n)=if(n==0,1,polcoeff(exp(sum(m=1,n,polcoeff((1-x)/(1-2*x-x^2+x*O(x^(m^2))),m^2)*x^m/m)+x*O(x^n)),n))}
    
  • PARI
    {a(n)=if(n==0,1,(1/n)*sum(k=1,n,polcoeff((1-x)/(1-2*x-x^2+x*O(x^(k^2))),k^2)*a(n-k)))}

Formula

a(n) == 1 (mod 8).
a(n) = (1/n)*Sum_{k=1..n} A002203(k^2)/2*a(n-k) for n>0 with a(0)=1.
Self-convolution yields A165937.
Showing 1-3 of 3 results.