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%I #8 Nov 18 2023 11:53:48
%S 4,10,15,20,24,30,40,44,50,60,64,65,70,80,84,90
%N List of numbers in the range 1 to 99 missing from A366487.
%C These numbers do not occur as differences between successive terms in A121805.
%H Carlos Rivera, <a href="https://www.primepuzzles.net/puzzles/puzz_980.htm">Puzzle 980. The "Commas" sequence</a>, The Prime Puzzles and Problems Connection.
%t a[1] = 1; a[n_] := a[n] = For[r = Mod[a[n - 1], 10]; y = 0, y <= 9, y++, If[y == IntegerDigits[#][[1]], Return[#]] &[a[n - 1] + 10 r + y]]; Complement[Range[99], Union@ Differences@ Array[a, 10^6]] (* _Michael De Vlieger_, Nov 18 2023, after _Jean-François Alcover_ at A121805 *)
%Y Cf. A121805, A366487.
%K nonn,base,fini,full
%O 1,1
%A _N. J. A. Sloane_, Nov 17 2023
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