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A318701 Tetrahedral numbers that are not divisible by any smaller tetrahedral number except 1. 2
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 (list; graph; refs; listen; history; text; internal format)
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: A059710 A149177 A149178 * 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

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Last modified May 10 22:16 EDT 2021. Contains 343780 sequences. (Running on oeis4.)