VOOZH about

URL: https://oeis.org/A072966

⇱ A072966 - OEIS

login
A072966
Numbers which are not the sum of two semiprimes.
10
0, 1, 2, 3, 4, 5, 6, 7, 9, 11, 17, 22, 33
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
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
Cf. A001358.
Sequence in context: A005577 A263362 A336733 * A363246 A245761 A371248
KEYWORD
nonn
AUTHOR
Lior Manor, Aug 13 2002
STATUS
approved