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A130440
Even pseudoprimes to base 31.
15
6, 10, 30, 66, 946, 3310, 10470, 36370, 60126, 104106, 128766, 170710, 323670, 369370, 398266, 596926, 813430, 1145166, 1494690, 2384866, 5960746, 6376126, 8178346, 18327310, 31380922, 34102630, 37105762, 40796526, 41950966, 41983446
OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..169 (terms below 10^11; terms 1..87 from Robert G. Wilson v)
Eric Weisstein's World of Mathematics, Fermat Pseudoprime.
MATHEMATICA
Do[ f=PowerMod[ 31, 2n-1, 2n ]; If[ f==1, Print[ 2n ] ], {n, 2, 500000} ]
lst = {}; Do[ If[ PowerMod[31, 2n - 1, 2n] == 1, AppendTo[lst, 2n]], {n, 2, 2^31}]; lst (* Robert G. Wilson v, Jun 01 2007 *)
PROG
(PARI) is(k) = k > 2 && !(k % 2) && Mod(31, k)^(k-1) == 1; \\ Amiram Eldar, Sep 29 2024
KEYWORD
nonn
AUTHOR
Alexander Adamchuk, May 26 2007
EXTENSIONS
More terms from Robert G. Wilson v, Jun 01 2007
STATUS
approved