A141579 Numbers n such that the arithmetic mean of the first n tribonacci numbers A000073 is an integer.

1, 2, 47, 53, 94, 103, 106, 163, 199, 206, 257, 269, 311, 326, 397, 398, 401, 419, 421, 499, 514, 538, 587, 599, 617, 622, 683, 757, 773, 794, 802, 838, 842, 863, 883, 907, 911, 929, 991, 998, 1021, 1087, 1109, 1123, 1174, 1181, 1198, 1210, 1234, 1237, 1291

Offset

1,2

Comments

Numbers in this sequence but not in A140973 are 2021 and 2090 (but no others below 8400). - Emeric Deutsch, Aug 19 2008.

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1500

Formula

{n: n | A008937(n-2)}.

Maple

A000073 := proc(n) option remember ; if n <= 1 then 0 ; elif n =2 then 1 ; else procname(n-1)+procname(n-2)+procname(n-3) ; fi; end: A008937 := proc(n) option remember ; add(A000073(i), i=0..n+1) ; end: isA := proc(n) if n = 1 then RETURN(true) ; fi; if A008937(n-2) mod n = 0 then true; else false ; fi; end: for n from 1 to 2000 do if isA(n) then printf("%d, ", n) ; fi; od ;

Mathematica

Module[{nn=1300, tnos}, tnos=LinearRecurrence[{1, 1, 1}, {0, 0, 1}, nn]; Position[ Table[Mean[Take[tnos, n]], {n, nn}], _?(IntegerQ[#]&)]]//Flatten (* Harvey P. Dale, Oct 05 2020 *)

Crossrefs

Cf. A000073, A008937, A140973.

Sequence in context: A273380 A124690 A195877 * A107205 A139839 A248862

Adjacent sequences: A141576 A141577 A141578 * A141580 A141581 A141582

Keyword

nonn

Author

R. J. Mathar, Aug 19 2008

Status

approved