

A199331


Number of ways to partition n into semiprimes.


2



0, 0, 0, 0, 0, 0, 0, 1, 0, 2, 0, 1, 2, 2, 2, 2, 0, 3, 4, 3, 2, 0, 2, 4, 4, 2, 2, 3, 4, 5, 6, 4, 0, 2, 6, 6, 4, 2, 6, 6, 4, 5, 8, 7, 4, 2, 8, 10, 6, 5, 2, 5, 6, 4, 10, 6, 4, 4, 10, 12, 12, 2, 6, 10, 6, 7, 8, 9, 6, 5, 12, 14, 10, 6, 6, 7, 8, 7, 10, 10, 6, 4, 14, 14
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,10


COMMENTS

Conjecture: Only the integers 1, 2, 3, 4, 5, 6, 7, 9, 11, 17, 22, 33 (A072966) cannot be partitioned into a set of two semiprimes.


LINKS

Table of n, a(n) for n=1..84.


MATHEMATICA

mx=200; semiPrimeQ[n_] := Plus @@ Last /@ FactorInteger@ n == 2; t = Select[ Range@ mx, semiPrimeQ]; s = Sort[Plus @@@ Tuples[t, 2]]; Transpose[ Tally@ Join[ Range@ mx, s]][[2]]  1


CROSSREFS

Cf. A035026.
Sequence in context: A007149 A028832 A260411 * A243917 A254212 A033773
Adjacent sequences: A199328 A199329 A199330 * A199332 A199333 A199334


KEYWORD

easy,nonn


AUTHOR

Robert G. Wilson v, Nov 05 2011


STATUS

approved



