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%I #22 Mar 28 2019 03:50:24
%S 5,14,20,21,35,42,70,84,91,119,133,140,158,168,182,189,217,231,238,
%T 245,266,280,287,315,329,336,364,378,385,413,427,434,462,476,483,511,
%U 518,525,532,560,574,581,609,623,630,658,672,679,686,707,721,728,756,770
%N Numbers not of the form x^2+2*y^2+7*z^2.
%C It appears that the only terms not divisible by 7 are 5, 29 and 158. - _Robert Israel_, Mar 27 2019
%H Robert Israel, <a href="/A306989/b306989.txt">Table of n, a(n) for n = 1..10000</a>
%H Irving Kaplansky, <a href="https://doi.org/10.1090/S0025-5718-1995-1265017-2">The first nontrivial genus of positive definite ternary forms</a>, Mathematics of Computation, Vol. 64 (1995): 341-345.
%p N:= 1000: # for terms <= N
%p V:= Array(0..N):
%p for x from 0 to floor(sqrt(N)) do
%p for y from 0 to floor(sqrt((N-x^2)/2)) do
%p for z from 0 do
%p v:= x^2 + 2*y^2 + 7*z^2;
%p if v > N then break fi;
%p V[v]:= 1;
%p od od od:
%p select(t -> V[t]=0, [$1..N]); # _Robert Israel_, Mar 27 2019
%K nonn
%O 1,1
%A _N. J. A. Sloane_, Mar 26 2019
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