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

1,1

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.

Links

Table of n, a(n) for n=1..34.

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 *)

Crossrefs

Cf. A136047.

Sequence in context: A252272 A247529 A301991 * A209373 A207076 A189181

Adjacent sequences: A136045 A136046 A136047 * A136049 A136050 A136051

Keyword

nonn

Author

Zak Seidov, Dec 12 2007

Status

approved