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A000350 Numbers n such that Fibonacci(n) ends with n.
(Formerly M3935 N1619)
7
0, 1, 5, 25, 29, 41, 49, 61, 65, 85, 89, 101, 125, 145, 149, 245, 265, 365, 385, 485, 505, 601, 605, 625, 649, 701, 725, 745, 749, 845, 865, 965, 985, 1105, 1205, 1249, 1345, 1445, 1585, 1685, 1825, 1925, 2065, 2165, 2305, 2405, 2501, 2545, 2645, 2785, 2885 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Conjecture: Other than 1 and 5, there is no n such that Fibonacci(n) in binary ends with n in binary. The conjecture holds up to n=50000. - Ralf Stephan, Aug 21 2006

The conjecture for binary numbers holds for n < 2^25. - T. D. Noe, May 14 2007

Conjecture is true. It is easy to prove (by induction on k) that if F(n) ends with n in binary, then n == 0, 1, or 5 modulo 3*2^k for any positive integer k, i.e., n must simply be equal to 0, 1, or 5. - Max Alekseyev, Jul 03 2009

REFERENCES

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

LINKS

T. D. Noe and Alois P. Heinz, Table of n, a(n) for n = 1..1034 (terms n = 1..803 from T. D. Noe)

M. Dunton and R. E. Grimm, Fibonacci on Egyptian fractions, Fib. Quart., 4 (1966), 339-354.

EXAMPLE

Fibonacci(25) = 75025 ends with 25.

MATHEMATICA

a=0; b=1; c=1; lst={}; Do[a=b; b=c; c=a+b; m=Floor[N[Log[10, n]]]+1; If[Mod[c, 10^m]==n, AppendTo[lst, n]], {n, 3, 5000}]; Join[{0, 1}, lst] (* edited and changed by Harvey P. Dale, Sep 10 2011 *)

fnQ[n_]:=Mod[Fibonacci[n], 10^IntegerLength[n]]==n; Select[Range[ 0, 2900], fnQ] (* Harvey P. Dale, Nov 03 2012 *)

PROG

(Haskell)

import Data.List (isSuffixOf, elemIndices)

import Data.Function (on)

a000350 n = a000350_list !! (n-1)

a000350_list = elemIndices True $

               zipWith (isSuffixOf `on` show) [0..] a000045_list

-- Reinhard Zumkeller, Apr 10 2012

(PARI) for(n=0, 1e4, if(((Mod([1, 1; 1, 0], 10^#Str(n)))^n)[1, 2]==n, print1(n", "))) \\ Charles R Greathouse IV, Apr 10 2012

CROSSREFS

Cf. A000045, A050816, A038546, A052000, A023172.

Sequence in context: A036137 A070380 A068574 * A000221 A018612 A036127

Adjacent sequences:  A000347 A000348 A000349 * A000351 A000352 A000353

KEYWORD

nonn,base,easy,nice

AUTHOR

N. J. A. Sloane

STATUS

approved

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Last modified July 24 03:48 EDT 2017. Contains 289717 sequences.