A278647 - OEIS

%I #21 Dec 11 2016 06:55:44

%S 5,3,2,2,3,5,1,3,1,4,1,2,2,1,1,4,5,1,1,1,2,3,2,1,4,3,2,3,1,1,3,2,2,3,

%T 2,2,1,1,4,2,3,1,1,2,1,1,3,1,1,2,2,1,1,2,1,2,1,2,5,5,1,1,3,3,2,1,2,1,

%U 1,3,2,1,1,2,1,4,1,4,1,3,1,1,3,2,1,1,1,2,2,3,3,1,1,2,3,2,1,1,1,3

%N First differences of Hypotenuse numbers A009003.

%C a(n) <= 5, since A009003 contains all multiples of 5. - _Robert Israel_, Dec 08 2016

%H Robert Israel, <a href="/A278647/b278647.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = A009003(n+1) - A009003(n).

%p L:= select(t -> has(numtheory:-factorset(t) mod 4,1), [$1..1000]):

%p L[2..-1]-L[1..-2]; # _Robert Israel_, Dec 08 2016

%t Differences@ Select[Range@ 208, Length@ PowersRepresentations[#^2, 2, 2] > 1 &] (* _Michael De Vlieger_, Nov 25 2016, after _Alonso del Arte_ at A009003 *)

%Y Cf. A009003.

%K nonn

%O 1,1

%A _Zhandos Mambetaliyev_, Nov 24 2016