login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A290159 Numerators of coefficients in Taylor series expansion of (1+x+x^2)^(1/2). 0
1, 1, 3, -3, 3, 15, -57, 21, 867, -1893, 1581, 8283, -76953, 34203, 361551, -869691, 6420387, 34130067, -167946159, 79445631, 1696170093, -4239570255, 4083041217, 21859150803, -442212416121, 215805655695, 2316081934929, -5909439428697, 11656013746863, 62663656767603, -322045194694305, 160129270032933, 27589357112530467 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

Denominators of the Taylor series expansion are given by A046161.

The terms after the second are divisible by 3.

The sequence of the absolute values is not monotonic.

LINKS

Table of n, a(n) for n=0..32.

MAPLE

a:= n-> numer(coeff(series(sqrt(1+x+x^2), x, n+3), x, n)):

seq(a(n), n=0..35);  # Alois P. Heinz, Jul 25 2017

MATHEMATICA

Numerator[CoefficientList[Series[Sqrt[1+x+x^2], {x, 0, 32}], x]]

PROG

(PARI) x = 'x + O('x^40); apply(x->numerator(x), Vec((1+x+x^2)^(1/2))) \\ Michel Marcus, Jul 24 2017

CROSSREFS

Cf. A046161 (denominators).

Sequence in context: A196529 A110668 A176248 * A356388 A083562 A332860

Adjacent sequences:  A290156 A290157 A290158 * A290160 A290161 A290162

KEYWORD

sign,frac

AUTHOR

Bruno Zürcher, Jul 22 2017

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified August 17 23:13 EDT 2022. Contains 356204 sequences. (Running on oeis4.)