The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A356809 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
Showing entries 1-10 | older changes

A356809

Fibonacci numbers which are not the sum of two squares.
(history; published version)

#24 by N. J. A. Sloane at Tue Jan 10 18:19:28 EST 2023

STATUS

proposed

approved

#23 by Chai Wah Wu at Tue Jan 10 14:33:55 EST 2023

STATUS

editing

proposed

#22 by Chai Wah Wu at Tue Jan 10 14:33:48 EST 2023

LINKS

Chai Wah Wu, <a href="/A356809/b356809.txt">Table of n, a(n) for n = 1..472</a>

STATUS

proposed

editing

#21 by Chai Wah Wu at Tue Jan 10 13:24:50 EST 2023

STATUS

editing

proposed

#20 by Chai Wah Wu at Tue Jan 10 13:24:45 EST 2023

PROG

if any(map(lambda d:d[0]p&3==3 and d[1]e&1, for p, e in factorint(a).items())):

STATUS

proposed

editing

#19 by Chai Wah Wu at Tue Jan 10 13:22:35 EST 2023

STATUS

editing

proposed

#18 by Chai Wah Wu at Tue Jan 10 13:22:32 EST 2023

PROG

(Python)

from itertools import islice

from sympy import factorint

def A356809_gen(): # generator of terms

a, b = 1, 2

while True:

if any(map(lambda d:d[0]&3==3 and d[1]&1, factorint(a).items())):

yield a

a, b = b, a+b

A356809_list = list(islice(A356809_gen(), 30)) # Chai Wah Wu, Jan 10 2023

STATUS

approved

editing

#17 by N. J. A. Sloane at Sun Sep 04 12:36:40 EDT 2022

STATUS

proposed

approved

#16 by Michel Marcus at Sun Sep 04 09:38:19 EDT 2022

STATUS

editing

proposed

#15 by Michel Marcus at Sun Sep 04 09:38:11 EDT 2022

PROG

(PARI) is(n)=if(n%4==3, return(1)); my(f=factor(n)); for(i=1, #f~, if(f[i, 1]%4==3 && f[i, 2]%2, return(1))); 0; \\ A022544

lista(nn) = select(is, apply(fibonacci, [1..nn])); \\ Michel Marcus, Sep 04 2022

STATUS

proposed

editing