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A109760 Composite n such that binomial(5*n,n) == 5^n (mod n). 2
4, 365, 400, 685, 3200, 6400, 12550, 12800, 16525, 25600, 51200, 225125, 70463125, 271094125, 431434441 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

No other terms below 10^9.

LINKS

Table of n, a(n) for n=1..15.

Max Alekseyev, PARI/GP scripts for various problems

EXAMPLE

4 is a term because binomial(5*4, 4) = 4845, 5^4 = 625 and 4845 mod 4 = 625 mod 4 = 1.

MATHEMATICA

Do[If[ !PrimeQ[n], If[Mod[Binomial[5*n, n], n] == Mod[5^n, n], Print[n]]], {n, 1, 50000}]

CROSSREFS

Cf. A080469.

Sequence in context: A215827 A051955 A177114 * A051181 A154682 A292195

Adjacent sequences:  A109757 A109758 A109759 * A109761 A109762 A109763

KEYWORD

hard,more,nonn

AUTHOR

Ryan Propper, Aug 12 2005

EXTENSIONS

a(12) from D. S. McNeil, Mar 15 2009

225125 from Max Alekseyev, Sep 13 2009

Three more terms from Max Alekseyev, Nov 06 2009

STATUS

approved

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Last modified September 26 10:59 EDT 2017. Contains 292518 sequences.