A136048 Semiprime terms in A136047.

185, 497, 511, 1041, 1059, 1903, 3107, 4705, 4735, 6817, 9481, 12761, 16721, 33379, 48961, 49027, 68857, 80561, 80639, 93521, 179503, 201241, 250097, 306281, 306403, 405551, 482161, 482303, 523921, 885631, 947939, 1081001, 1081187, 1226177

Offset: 1

Author

Zak Seidov, Dec 12 2007

Keywords

• nonn

Comments

185 = 5*37, 497 = 7*71, 511 = 7*73, 1041 = 3*347, 1059 = 3*353, 1903 = 11*173, 3107 = 13*239, 4705 = 5*941, 4735 = 5*947, 6817 = 17*401, 9481 = 19*499, 12761 = 7*1823, 16721 = 23*727, 33379 = 29*1151, 48961 = 11*4451, 49027 = 11*4457, 68857 = 37*1861, 80561 = 13*6197, 80639 = 13*6203, 93521 = 41*2281.

Positions of a(n) in A136047 are given in A135439.

Crossrefs

Cf. A136047.

Programs

Mathematica

a[1]=1;a[n_]:=a[n]=a[n-1]+n^(1+Mod[n,2]);A136047=Table[a[n],{n,1000}]; A136048=Select[A136047,Total[Last/@FactorInteger[ # ]]==2&]
nxt[{n_,a_}]:={n+1,If[OddQ[n],a+n+1,a+(n+1)^2]}; Select[ Transpose[ NestList[ nxt,{1,1},200]][[2]],PrimeOmega[#]==2&] (* Harvey P. Dale, Oct 11 2015 *)