A358311 Lucas numbers that are not the sum of two squares.
3, 7, 11, 47, 76, 123, 199, 322, 843, 1364, 2207, 3571, 5778, 15127, 24476, 39603, 64079, 103682, 167761, 271443, 439204, 710647, 1149851, 4870847, 7881196, 12752043, 20633239, 33385282, 87403803, 141422324, 228826127, 370248451, 599074578, 1568397607, 2537720636
Offset: 1
Keywords
Links
- Chai Wah Wu, Table of n, a(n) for n = 1..958
Programs
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Maple
R:= NULL: count:= 0: a:= 2: b:= 1: for i from 1 while count < 100 do a, b:= b,a+b; if ormap(t -> t[2]::odd and t[1] mod 4 = 3, ifactors(b)[2]) then R:= R, b; count:= count+1 fi od: R; # Robert Israel, Jan 10 2023 -
Python
from sympy import factorint from itertools import islice def A358311_gen(): # generator of terms a, b = 2,1 while True: if any(e&1 and p&3==3 for p, e in factorint(a).items()): yield a a, b = b, a+b A358311_list = list(islice(A358311_gen(),40))
Formula
phi^n < a(n) < phi^(2n) for n > 4. - Charles R Greathouse IV, Jan 11 2023
Comments