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A299156 Numbers k such that k*(k+1) divides tribonacci(k) (A000073(k)). 1
1, 256, 397, 1197, 8053, 8736, 9901, 32173, 33493, 33757, 38461, 48757, 56101, 57073, 64153, 76561, 79693, 87517, 100608, 102217, 105253, 105601, 105913, 105997, 107713, 108553, 110976, 116293, 123121, 131437, 138517, 143137, 147541, 151237, 156601, 171253 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

A subsequence of A232570.

LINKS

Chai Wah Wu, Table of n, a(n) for n = 1..10000 (n = 1..1000 from Alois P. Heinz)

EXAMPLE

tribonacci(256) = 10285895715599251294835119279496333059462348558276025598603904254464 = 256 * 257 * 156339611436029476149609668037091638184921397104146789862048642.

MAPLE

with(LinearAlgebra[Modular]):

T:= (n, m)-> MatrixPower(m, Mod(m, <<0|1|0>,

    <0|0|1>, <1|1|1>>, float[8]), n)[1, 3]:

a:= proc(n) option remember; local i, k, ok;

      if n=1 then 1 else

        for k from 1+a(n-1) do ok:= true;

          for i in ifactors(k*(k+1))[2] while ok do

            ok:= is(T(k, i[1]^i[2])=0)

          od; if ok then break fi

        od; k

      fi

    end:

seq(a(n), n=1..10);  # Alois P. Heinz, Feb 06 2018

MATHEMATICA

a = b = 0; c = d = 1; k = 2; lst = {1}; While[k < 171255, If[ Mod[c, k (k + 1)] == 0, AppendTo[lst, k]]; a = b; b = c; c = d; d = a + b + c; k++] (* Robert G. Wilson v, Feb 07 2018 *)

CROSSREFS

Cf. A000073, A217738, A232570, A274518.

Sequence in context: A114987 A046310 A115176 * A221259 A223693 A223064

Adjacent sequences:  A299153 A299154 A299155 * A299157 A299158 A299159

KEYWORD

nonn

AUTHOR

Seiichi Manyama, Feb 04 2018

STATUS

approved

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Last modified July 31 02:33 EDT 2021. Contains 346367 sequences. (Running on oeis4.)