A173966 Sums of two consecutive semiprimes.

19, 29, 43, 51, 67, 69, 77, 115, 171, 173, 187, 189, 237, 243, 245, 267, 283, 285, 291, 317, 355, 403, 405, 411, 427, 429, 435, 437, 507, 597, 603, 605, 653, 669, 723, 763, 787, 789, 891, 893, 907, 963, 1003, 1029, 1053, 1075, 1085, 1107, 1131, 1245, 1267

Offset: 1

Author

Vladimir Joseph Stephan Orlovsky, Mar 03 2010

Keywords

• nonn

Comments

First 16 terms:19,29,43,51,67,69,77,115,171,173,187,189,237,243,245,267 are the same as in A157483.

These are sums of two consecutive integers which are both semiprimes, whereas A118717 are sums of two semiprimes which are adjacent (consecutive) in A001358. [From R. J. Mathar, Mar 18 2010]

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000

Programs

Mathematica

f[n_]:=Last/@FactorInteger[n]=={1,1}||Last/@FactorInteger[n]=={2};lst={};Do[If[f[n],If[f[n+1],AppendTo[lst,2*n+1]]],{n,7!}];lst
Total/@Select[Partition[Select[Range[700],PrimeOmega[#]==2&],2,1],#[[2]]- #[[1]] == 1&] (* Harvey P. Dale, Jun 22 2020 *)