A318701 Tetrahedral numbers that are not divisible by any smaller tetrahedral number except 1.

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

Offset

1,2

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Example

4 is a term because it is divisible by 1.
10 is a term because it is divisible by 1 but not by 4.

Maple

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:
1, Res; # Robert Israel, Dec 28 2018

Mathematica

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 *)

Prog

(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

Crossrefs

Cf. A000292, A319788.

Sequence in context: A149177 A149178 A344559 * A152916 A222506 A108596

Adjacent sequences: A318698 A318699 A318700 * A318702 A318703 A318704

Keyword

nonn

Author

Torlach Rush, Aug 31 2018

Extensions

a(1) = 1 inserted by Michel Marcus, Nov 09 2018

Status

approved