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A127315
Numbers n such that n^4 divides 19^(n^2)-1.
0
1, 2, 3, 6, 42, 78, 546, 1806, 23478
OFFSET
1,2
COMMENTS
a(n)^2 are the perfect squares in A128399.
a(10) > 10^13. [From Max Alekseyev]
MATHEMATICA
Do[g=PowerMod[19, n^2, n^4]-1; If[IntegerQ[g/n^4], Print[n]], {n, 1, 10000}]
CROSSREFS
Cf. A128399 = numbers n such that n^2 divides 19^n-1.
Sequence in context: A374464 A018354 A124045 * A018359 A274805 A049383
KEYWORD
hard,more,nonn
AUTHOR
Alexander Adamchuk, Mar 28 2007
EXTENSIONS
a(9) from D. S. McNeil, Mar 02 2009
STATUS
approved