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A318701
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Tetrahedral numbers that are not divisible by any smaller tetrahedral number except 1.
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2
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1, 4, 10, 35, 165, 286, 969, 1771, 2925, 3654, 4495, 9139, 12341, 16215, 23426, 32509, 39711, 47905, 52394, 67525, 79079, 91881, 105995, 129766, 138415, 156849, 176851, 209934, 221815, 246905, 273819, 302621, 366145, 383306, 437989, 477191, 540274, 562475, 657359, 708561, 762355, 848046, 939929, 1004731
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OFFSET
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1,2
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LINKS
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EXAMPLE
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4 is a term because it is divisible by 1.
10 is a term because it is divisible by 1 but not by 4.
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MAPLE
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count:= 1: Res:= NULL:
for i from 2 while count < 100 do
r:= i*(i+1)*(i+2)/6;
if not ormap(t -> (r/t)::integer, [Res]) then
Res:= Res, r;
count:= count+1;
fi
od:
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MATHEMATICA
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t[n_]:=n(n+1)(n+2)/6; tQ[n_] := Module[{ans=True, tn=t[n]}, Do[If[Divisible[tn, t[i]], ans=False; Break[]], {i, 2, n-1}]; ans]; t[Select[Range[100], tQ]] (* Amiram Eldar, Nov 14 2018 *)
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PROG
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(PARI) t(n) = n*(n+1)*(n+2)/6;
isok(n) = my(tn=t(n)); for(i=2, n-1, if (!(tn % t(i)), return (0))); return (1);
lista(nn) = for (n=1, nn, if (isok(n), print1(t(n), ", "))); \\ Michel Marcus, Sep 29 2018
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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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