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A109769 Composite n such that binomial(7*n, n) == 7^n (mod n). 2
18, 25, 133, 2107, 4676, 226037, 4477739, 827867201 (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..8.

Max Alekseyev, PARI/GP scripts for various problems

EXAMPLE

18 is a term because binomial(7*18, 18) = 2797093093529137508875, 7^18 = 1628413597910449 and 2797093093529137508875 mod 18 = 1628413597910449 mod 18 = 1.

MATHEMATICA

Do[If[ !PrimeQ[n], If[Mod[Binomial[7*n, n], n] == Mod[7^n, n], Print[n]]], {n, 2, 20000}]

CROSSREFS

Cf. A080469.

Sequence in context: A003300 A245022 A248111 * A229967 A212049 A212052

Adjacent sequences:  A109766 A109767 A109768 * A109770 A109771 A109772

KEYWORD

more,nonn

AUTHOR

Ryan Propper, Aug 13 2005

EXTENSIONS

226037 from Max Alekseyev, Sep 13 2009

Two more terms from Max Alekseyev, Nov 06 2009

STATUS

approved

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Last modified December 10 15:09 EST 2019. Contains 329896 sequences. (Running on oeis4.)