A123093 Numbers which are not the sum of two 3-almost primes.

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

Author

Jonathan Vos Post, Sep 27 2006

Keywords

• easy
• fini
• full
• nonn

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

Crossrefs

Cf. A014612, A072966.

Programs

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 *)

Formula

Complement of Sumset {A014612} + {A014612}.

Extensions

Edited by T. D. Noe, Nov 06 2006