login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A112374 Let T(n) = A000078(n+2), n >= 1; a(n) = smallest k such that n divides T(k). 0
1, 3, 6, 4, 6, 9, 8, 5, 9, 13, 20, 9, 10, 8, 6, 10, 53, 9, 48, 28, 18, 20, 35, 18, 76, 10, 9, 8, 7, 68, 20, 15, 20, 53, 30, 9, 58, 48, 78, 28, 19, 18, 63, 20, 68, 35, 28, 18, 46, 108, 76, 10, 158, 9, 52, 8, 87, 133, 18, 68, 51, 20, 46, 35, 78, 20, 17, 138, 35, 30, 230, 20, 72, 58, 76 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Rank of apparition of n in the tetranacci numbers. - T. D. Noe, Dec 05 2005

This sequence is well-defined. Proof by T. D. Noe: for every prime p, Brenner proves we can find k(p) such that p divides the k(p)-th term of n-step Fibonacci. Using Brenner's methods, we know that p will also divide every j*k(p)-th term of the sequence for any j>0. We use this last fact to go to the general case: For integer m, we can find a term that m divides as follows: (1) factor m into primes: m = p1^e1 p2^e2...pr^er, (2) let K = m k(p1) k(p2)...k(pr) / (p1 p2 ... pr) (3) then m will divide the K-th term of the sequence. In general, K is much too large. However, it does show that every prime divides a term of every n-step Fibonacci sequence for n>1. - T. D. Noe, Dec 05 2005

LINKS

Table of n, a(n) for n=1..75.

J. L. Brenner, Linear Recurrence Relations, Amer. Math. Monthly, Vol. 61 (1954), 171-173.

T. D. Noe and J. V. Post, Primes in Fibonacci n-step and Lucas n-Step Sequences, J. Integer Seq. 8, Article 05.4.4, 2005.

Eric Weisstein's World of Mathematics, Tetranacci Number.

Eric Weisstein's World of Mathematics, Fibonacci n-Step Number.

FORMULA

a(n) = Min{k: n | A000078(k)}.

MATHEMATICA

n=4; Table[a=Join[{1}, Table[0, {n-1}]]; k=0; While[k++; s=Mod[Plus@@a, i]; a=RotateLeft[a]; a[[n]]=s; s!=0]; k, {i, 100}] (* T. D. Noe, Dec 05 2005 *)

CROSSREFS

Cf. A000078, A112269, A112305.

Sequence in context: A073233 A011287 A090963 * A222409 A093064 A197568

Adjacent sequences:  A112371 A112372 A112373 * A112375 A112376 A112377

KEYWORD

easy,nonn

AUTHOR

Jonathan Vos Post, Dec 02 2005

EXTENSIONS

Corrected by T. D. Noe, Dec 05 2005

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified July 17 18:47 EDT 2019. Contains 325109 sequences. (Running on oeis4.)