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A140488
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Trajectory of 5 under repeated application of the map: n -> n + second-smallest number that does not divide n.
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8
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5, 8, 13, 16, 21, 25, 28, 33, 37, 40, 46, 50, 54, 59, 62, 66, 71, 74, 78, 83, 86, 90, 97, 100, 106, 110, 114, 119, 122, 126, 131, 134, 138, 143, 146, 150, 157, 160, 166, 170, 174, 179, 182, 186, 191, 194, 198, 203, 206, 210, 218, 222, 227, 230, 234, 239, 242, 246
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listen;
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OFFSET
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1,1
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LINKS
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FORMULA
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It appears that a(n+98) = a(n)+420 for n >= 9. - Robert Israel, Oct 19 2021
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MAPLE
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f:= proc(n) local k, c;
c:= 0:
for k from 2 do
if n mod k <> 0 then
if c = 1 then return n+k fi;
c:= 1;
fi
od
end proc:
R:= 5: t:= 5:
for count from 2 to 100 do
t:= f(t);
R:= R, t;
od:
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MATHEMATICA
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a = {5}; Do[AppendTo[a, a[[ -1]] + Select[Range[a[[ -1]]], Mod[a[[ -1]], # ] > 0 &][[2]]], {60}]; a (* Stefan Steinerberger, Jul 01 2008 *)
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PROG
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(Python)
def aupton(terms):
alst = [5]
while len(alst) < terms:
an, k, smallest = alst[-1], 2, False
while not smallest or an%k == 0:
if not smallest and an%k != 0: smallest = True
k += 1
alst.append(an+k)
return alst
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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