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A090820 Composite n such that Fibonacci(n) == Legendre(n,5) (mod n). +0
4
25, 60, 120, 125, 180, 240, 300, 360, 480, 540, 600, 625, 660, 720, 840, 900, 960, 1080, 1200, 1320, 1440, 1500, 1620, 1680, 1800, 1860, 1920, 1980, 2160, 2400, 2460, 2520, 2640, 2700, 2760, 2880, 3000, 3060, 3125, 3240, 3300, 3360, 3420 (list; graph; listen)
OFFSET

1,1

COMMENT

If n is a prime, not 5, then Fibonacci(n) == Legendre(n,5) (mod n) (see for example G. H. Hardy and E. M. Wright, Theory of Numbers).

REFERENCES

Yorinaga, Masataka; On a congruencial property of Fibonacci numbers-considerations and remarks. Math. J. Okayama Univ. 19 (1976/77), no. 1, 11-17.

Yorinaga, Masataka; On a congruencial property of Fibonacci numbers-numerical experiments. Math. J. Okayama Univ. 19 (1976/77), no. 1, 5-10.

LINKS

F. J. van de Bult, D. C. Gijswijt, J. P. Linderman, N. J. A. Sloane and A. R. Wilks, A Slow-Growing Sequence Defined by an Unusual Recurrence, J. Integer Sequences, Vol. 10 (2007), #07.1.2.

F. J. van de Bult, D. C. Gijswijt, J. P. Linderman, N. J. A. Sloane and A. R. Wilks, A Slow-Growing Sequence Defined by an Unusual Recurrence [pdf, ps].

MATHEMATICA

Select[ Range[ 2, 5000 ], ! PrimeQ[ # ] && Mod[ Fibonacci[ # ] - JacobiSymbol[ #, 5 ], # ] == 0 & ]

CROSSREFS

Cf. A049062, A093372, A094063.

Sequence in context: A125827 A163654 A063317 this_sequence A044127 A044508 A166873

Adjacent sequences: A090817 A090818 A090819 this_sequence A090821 A090822 A090823

KEYWORD

nonn

AUTHOR

Eric S Rowland (erowland(AT)math.rutgers.edu), Apr 29 2004

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Last modified December 18 21:37 EST 2009. Contains 171024 sequences.


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