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.
Taking 79 as an example; 7^3+9^3=1072, 1^3+0^3+7^3+2^3=352, 3^3+5^3+2^3=160, 1^3+6^3+0^3=217, 2^3+1^3+7^3=352. a(15)=229: 229 -> 2*2^3+9^3=745 -> 7^3+4^3+5^3+1=532 -> 5^3+3^3+2^3=160 -> 217 -> 352 -> 160 ... .
okQ[n_]:=MemberQ[NestList[Total[IntegerDigits[#]^3]&,n,20],160]; Select[Range[1200],okQ] (* Harvey P. Dale, Jun 20 2011 *)
Taking 40 for example, 4^3 + 0^3 = 64; 6^3 + 4^3 = 280; 2^3 + 8^3 + 0^3 = 520; 5^3 + 2^3 + 0^3 = 133; 1^3 + 3^3 + 3^3 = 55; 5^3 + 5^3 = 250.
A055012 := proc(n) local a,d ; a := 0 ; for d in convert(n,base,10) do a := a+d^3; od; a ; end: isA154820 := proc(n) local traj,t ; t := n ; traj := {} ; while true do if t in traj then if t in {133,55,250} then RETURN(true) ; else RETURN(false) ; fi; else traj := traj union {t} ; t := A055012(t) ; fi; od: end: for n from 1 to 1000 do if isA154820(n) then printf("%d,",n) ; fi; od: # R. J. Mathar, Jan 18 2009
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