login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A162841 G.f.: A(x) = sqrt( Sum_{n>=0} 4^(n(n+1)/2)*x^n ). 1
1, 2, 30, 1988, 519862, 535771548, 2197934140524, 36024384044050824, 2361111125528468202534, 618965296335059538851784236, 649035869315354547057886734224068, 2722257637277195404313634492141394601400, 45671920722055969331642704395417211607924522812 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Andrew Howroyd, Table of n, a(n) for n = 0..50

EXAMPLE

G.f.: A(x) = 1 + 2*x + 30*x^2 + 1988*x^3 + 519862*x^4 +...

A(x)^2 = 1 + 4*x + 64*x^2 + 4096*x^3 + 1048576*x^4 +...+ 4^(n(n+1)/2)*x^n +...

PROG

(PARI) {a(n)=polcoeff(sum(k=0, n, 4^(k*(k+1)/2)*x^k +x*O(x^n))^(1/2), n)}

CROSSREFS

Sequence in context: A208093 A144501 A198861 * A158260 A099800 A099929

Adjacent sequences:  A162838 A162839 A162840 * A162842 A162843 A162844

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Jul 14 2009

EXTENSIONS

Terms a(11) and beyond from Andrew Howroyd, Nov 08 2019

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified January 25 19:09 EST 2020. Contains 331249 sequences. (Running on oeis4.)