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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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS a(n)^2 are the perfect squares in A128399. a(10) > 10^13. [From Max Alekseyev] LINKS 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: A184716 A018354 A124045 * A018359 A274805 A049383 Adjacent sequences:  A127312 A127313 A127314 * A127316 A127317 A127318 KEYWORD hard,more,nonn AUTHOR Alexander Adamchuk, Mar 28 2007 EXTENSIONS a(9) from D. S. McNeil, Mar 02 2009 STATUS approved

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Last modified December 12 12:50 EST 2019. Contains 329958 sequences. (Running on oeis4.)