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A147857 Differences of two positive 4th powers.

%I A147857 #16 Jan 16 2025 23:07:12
%S A147857 0,15,65,80,175,240,255,369,544,609,624,671,1040,1105,1215,1280,1295,
%T A147857 1695,1776,2145,2320,2385,2400,2465,2800,3439,3471,3840,4015,4080,
%U A147857 4095,4160,4641,5265,5904,5936,6095,6305,6480,6545,6560,7599,7825,8080,8704
%N A147857 Differences of two positive 4th powers.
%C A147857 If n belongs to this sequence then so does n*m^4 for any positive integer m. Primitive elements (i.e., not of the form n*m^4 for m>1) are listed in A147858.
%C A147857 There is no square in this sequence except 0. - _Altug Alkan_, Apr 08 2016
%H A147857 Robert Israel, <a href="/A147857/b147857.txt">Table of n, a(n) for n = 1..10000</a>
%p A147857 N:= 10^4: # to get all terms <= N
%p A147857 Res:= {0}:
%p A147857 for a from 1 to floor(sqrt(N-2)) do
%p A147857   if a^4 > N then bmin:= ceil((a^4-N)^(1/4)) else bmin:= 1 fi;
%p A147857   Res:= Res union {seq(a^4-b^4, b=bmin..a-1)}
%p A147857 od:
%p A147857 sort(convert(Res,list)); # _Robert Israel_, Sep 28 2018
%t A147857 nn = 50; Take[Union @@ Map[Differences, Union@ Map[Sort@ # &, Tuples[Range[Ceiling[nn/3]], {2}]]^4], nn] (* _Michael De Vlieger_, Apr 09 2016 *)
%Y A147857 Subsequence of A152044.
%Y A147857 Cf. A147854, A147856, A147858
%K A147857 nonn
%O A147857 1,2
%A A147857 _Max Alekseyev_, Nov 15 2008, Nov 19 2008
%E A147857 Offset changed by _Robert Israel_, Sep 28 2018