OFFSET
1,4
COMMENTS
From Robert Israel, Aug 20 2017: (Start)
-3 <= a(n) <= 3.
It appears that:
a(n) = -3 if and only if a(n+1) = 3.
if a(n) = -2 then a(n+1) = 0, 1 or 2.
if a(n) = -1 or 0 then a(n+1) = -1, 0, 1 or 2.
if a(n) = 1 then a(n+1) = -3, -1, 0 or 1.
if a(n) = 2 then a(n+1) = -3 or -2.
if a(n) = 3 then a(n+1) = -2 or -1.
(End)
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
FORMULA
a(n) = {Pi*(n+3)^2} - 3*{Pi*(n+2)^2} + 3*{Pi*(n+1)^2} - {Pi*n^2}.
MAPLE
A0:= [seq(frac(Pi*n^2), n=1..103)]:
A1:= A0[2..-1]-A0[1..-2]:
A2:= A1[2..-1]-A1[1..-2]:
A2[2..-1]-A2[1..-2]; # Robert Israel, Aug 20 2017
MATHEMATICA
Differences[FractionalPart[Pi*Range[100]^2], 3] (* Paolo Xausa, Feb 23 2024 *)
CROSSREFS
KEYWORD
sign
AUTHOR
Simon Plouffe, Aug 20 2017
STATUS
approved