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!)
A185457 a(n) = abs( Im((2+i)^(2^n)) ). 2
1, 4, 24, 336, 354144, 116749235904, 22940770664883067253376, 182503181432559739767250904458105698387204864 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

The next term is too large to be displayed here.

Old name was: Leg of primitive Pythagorean triangle generated by repeated application of the basic formula y(n) = 2*x(n-1)*y(n-1), x(1)=2, y(1)=1.

LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..11

FORMULA

a(n) = abs( Im((2+i)^(2^n)) ).

EXAMPLE

y(2)=24 since x(1)=3, y(1)=4 are the two legs of Pythagorean triangle obtained by p=2, q=1; second iteration p=3, q=4 gives 2*3*4=24.

MAPLE

a:= n-> abs(Im((2+I)^(2^n))):

seq(a(n), n=0..8);  # Alois P. Heinz, Apr 25 2013

MATHEMATICA

Table[Abs[Im[(2 + I)^(2^n)]], {n, 0, 10}] (* G. C. Greubel, Jul 07 2017 *)

PROG

(PARI) a(n) = abs(imag((2+I)^(2^n))); \\ Joerg Arndt, Apr 25 2013

(Python)

from sympy import im, I

def a(n): return abs(im((2 + I)**(2**n)))

print([a(n) for n in range(11)]) # Indranil Ghosh, Jul 08 2017

CROSSREFS

Cf. A176594, A120905.

Cf. A099456 ( imaginary part of (2+i)^n ).

Sequence in context: A005756 A206239 A196687 * A024250 A167140 A010572

Adjacent sequences:  A185454 A185455 A185456 * A185458 A185459 A185460

KEYWORD

nonn,less

AUTHOR

Carmine Suriano, Feb 04 2011

EXTENSIONS

Better name from Joerg Arndt, Apr 25 2013

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 November 29 14:50 EST 2021. Contains 349416 sequences. (Running on oeis4.)