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A123093
Numbers which are not the sum of two 3-almost primes.
0
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 17, 18, 19, 21, 22, 23, 25, 27, 29, 31, 33, 34, 37, 41, 43, 44, 49, 51, 59, 61, 66, 67, 85, 99, 101, 109, 163
OFFSET
1,2
COMMENTS
3-almost prime analog of A072966, numbers which are not the sum of two semiprimes. In general, it seems that almost all even numbers can be written as the sum of two k-almost primes for any positive integer k. - T. D. Noe, Nov 06 2006
FORMULA
Complement of Sumset {A014612} + {A014612}.
MATHEMATICA
nn=10000; t3=Select[Range[2, nn], Plus@@Last/@FactorInteger[ # ]==3&]; t3sum=Table[0, {nn}]; Do[n=t3[[i]]+t3[[j]]; If[n<=nn, t3sum[[n]]=1], {i, Length[t3]}, {j, i, Length[t3]}]; Flatten[Position[t3sum, 0]] (* T. D. Noe, Nov 06 2006 *)
CROSSREFS
Sequence in context: A337379 A121684 A191853 * A191932 A044920 A330938
KEYWORD
easy,fini,full,nonn
AUTHOR
Jonathan Vos Post, Sep 27 2006
EXTENSIONS
Edited by T. D. Noe, Nov 06 2006
STATUS
approved