

A306989


Numbers not of the form x^2+2*y^2+7*z^2.


1



5, 14, 20, 21, 35, 42, 70, 84, 91, 119, 133, 140, 158, 168, 182, 189, 217, 231, 238, 245, 266, 280, 287, 315, 329, 336, 364, 378, 385, 413, 427, 434, 462, 476, 483, 511, 518, 525, 532, 560, 574, 581, 609, 623, 630, 658, 672, 679, 686, 707, 721, 728, 756, 770
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OFFSET

1,1


COMMENTS

It appears that the only terms not divisible by 7 are 5, 29 and 158.  Robert Israel, Mar 27 2019


LINKS



MAPLE

N:= 1000: # for terms <= N
V:= Array(0..N):
for x from 0 to floor(sqrt(N)) do
for y from 0 to floor(sqrt((Nx^2)/2)) do
for z from 0 do
v:= x^2 + 2*y^2 + 7*z^2;
if v > N then break fi;
V[v]:= 1;
od od od:


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



