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A158564 Generalized Fibonacci numbers round(abs(Fib(n*I))), I=sqrt(-1). 1
0, 5, 120, 2771, 64120, 1483771, 34335480, 794546793, 18386363119, 425473177569, 9845744025606, 227837336237557, 5272313768144476, 122004992372201577, 2823280028149695952, 65332655347676516331, 1511842896283885073147 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Generalized Fib(x) = (phi^x - cos(x*Pi) / phi^x) / sqrt(5) where phi = (1 + sqrt(5))/2.

LINKS

Harry J. Smith, Table of n, a(n) for n = 0..100

Harry J. Smith, Generalized Fibonacci numbers

EXAMPLE

a(2) = 120 because Fib(2*I) = -68.179... + 98.623... * I, whose absolute value is 119.895..., and rounded gives 120.

PROG

(PARI) { default(realprecision, 150); s5 = sqrt(5); phi = (1 + s5)/2.0; for (n=0, 100, x=n*I; f = round(abs((phi^x - cos(x*Pi) / phi^x) / s5)); write("b158564.txt", n, " ", f)) }

CROSSREFS

Sequence in context: A307350 A322707 A160695 * A252928 A308363 A192639

Adjacent sequences:  A158561 A158562 A158563 * A158565 A158566 A158567

KEYWORD

nonn

AUTHOR

Harry J. Smith, Mar 21 2009

STATUS

approved

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Last modified May 11 13:21 EDT 2021. Contains 343791 sequences. (Running on oeis4.)