

A007536


Numbers that are not the sum of 3 hexagonal numbers (probably finite).
(Formerly M3244)


5



4, 5, 9, 10, 11, 14, 19, 20, 23, 24, 25, 26, 32, 33, 37, 38, 39, 41, 42, 48, 50, 53, 54, 55, 59, 63, 64, 65, 69, 70, 76, 77, 80, 83, 85, 86, 89, 99, 102, 104, 108, 110, 113, 114, 115, 116, 123, 124, 128, 129, 130, 131, 140, 143, 144, 145, 146, 152, 161, 162, 167
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OFFSET

1,1


COMMENTS

Jud McCranie remarks that a(638) = 146858 is probably the last term.


REFERENCES

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).


LINKS



MATHEMATICA

notSumQ[n_] := Reduce[0 <= x <= y <= z && n == x*(2x  1) + y*(2y  1) + z*(2z  1), {x, y, z}, Integers] === False; A007536 = Reap[ Do[ If[notSumQ[n], Print[n]; Sow[n]], {n, 1, 135}]][[2, 1]] (* JeanFrançois Alcover, Jun 27 2012 *)


PROG

(MATLAB)
N = 10^7; % to get all terms up to N
M = floor((sqrt(1+8*N)+1)/4);
H = zeros(1, N);
H((1:M) .*(2*(1:M)1)) = 1;
H2 = conv(H, H);
H2 = H2(1:N);
H3 = conv(H, H2);
HS = H(3:N) + H2(2:N1) + H3(1:N2);


CROSSREFS



KEYWORD

nonn,fini,nice


AUTHOR



EXTENSIONS



STATUS

approved



