cp's OEIS Frontend

A027564 Numbers not of form abcd + abce + abde + acde + bcde for 1 <= a <= b <= c <= d <= e.

%I A027564 #13 Jan 09 2025 19:15:56
%S A027564 1,2,3,4,6,7,8,10,11,12,14,15,18,19,20,22,24,26,27,31,32,34,35,36,38,
%T A027564 39,42,46,47,50,54,55,59,60,62,66,67,70,71,75,78,84,87,90,92,94,98,99,
%U A027564 102,104,106,110,111,115,116,119,122,126,127,130,131,132,138
%N A027564 Numbers not of form abcd + abce + abde + acde + bcde for 1 <= a <= b <= c <= d <= e.
%H A027564 Robert Israel, <a href="/A027564/b027564.txt">Table of n, a(n) for n = 1..1578</a>
%p A027564 N := 1000: # for all terms <= N
%p A027564 V:= Vector(N):
%p A027564 for a from 1 to floor((N/5)^(1/4)) do
%p A027564   for b from a while 4*a*b^3+b^4<= N do
%p A027564     for c from b while 3*a*b*c^2 + (a+b)*c^3 <= N do
%p A027564       for d from c while 2*a*b*c*d + (b*c+a*c+a*b)*d^2 <= N do
%p A027564         for e from d do
%p A027564           r:= a*b*c*d+a*b*c*e+a*b*d*e+a*c*d*e+b*c*d*e;
%p A027564           if r > N then break fi;
%p A027564           V[r]:= 1;
%p A027564 od od od od od:
%p A027564 select(t -> V[t]=0, [$1..N]); # _Robert Israel_, Nov 04 2018
%Y A027564 Cf. A025052 (3 variables), A027563 (4 variables), A027565, A027566.
%K A027564 nonn,fini
%O A027564 1,2
%A A027564 _R. H. Hardin_