

A072966


Numbers which are not the sum of two semiprimes.


10



0, 1, 2, 3, 4, 5, 6, 7, 9, 11, 17, 22, 33
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OFFSET

1,3


COMMENTS

Is this sequence finite?
See the graph of sequence A072931 for compelling evidence that 33 is the last term of this sequence.  T. D. Noe, Apr 11 2007


LINKS



EXAMPLE

a(10) = 11 since there is no way to represent 11 as a sum of two semiprimes. 13 is not a term since 13 = 4 + 9.


MATHEMATICA

lim = 10000;
s = Select[Range[lim], PrimeOmega[#] == 2 &];
c = Map[Total, Union[Subsets[s, {2}], Table[{s[[i]], s[[i]]}, {i, 1, Length[s]}]]];
Join[Complement[Range[0, lim], c], ">", lim ](* Robert Price, Mar 30 2019 *)


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



