This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
nxt[{a_,b_,c_}]:=With[{ir=IntegerReverse},{b,c,ir[ir[a]+ir[b]+ir[c]]}]; Select[NestList[nxt,{0,0,1},200][[;;,1]],PrimeOmega[#]==2&] (* Harvey P. Dale, Jul 22 2025 *)
nxt[{a1_,a2_,a3_}]:={a2,a3,a3+FromDigits[Reverse[IntegerDigits[a1]]]+ FromDigits[Reverse[IntegerDigits[a2]]]}; Flatten[Position[Transpose[ NestList[nxt,{0,0,1},200]][[1]],?(PrimeOmega[#]==2&)]]-1 (* _Harvey P. Dale, Oct 17 2012 *)
nxt[{a_,b_,c_}]:={b,c,IntegerReverse[c]+b+a};Flatten[Position[ NestList[ nxt,{0,0,1},200][[All,1]],?(PrimeOmega[#]==2&)]]-1 (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale, May 16 2018 *)
nxt[{a_,b_,c_}]:={b,c,Total[IntegerReverse/@{a,b,c}]};Flatten[ Position[ NestList[nxt,{0,0,1},220][[All,1]],?(PrimeOmega[#] == 2&)]]-1 (* _Harvey P. Dale, Dec 30 2018 *)