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A119678 a(n) = least k such that the remainder when 4^k is divided by k is n. 46
3, 14, 137243, 5, 6821, 10, 57, 124, 35, 18, 2791496231, 244, 51, 505, 199534799, 20, 30271293169, 49, 45, 236, 399531841, 42, 533, 25, 39, 50, 352957, 36, 995, 98, 33, 112, 47503, 55, 42345881, 44, 2981, 289, 805, 78, 1019971289, 25498, 2121, 212 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(n) > n.

Numbers n>1 such that a(n-1) = n are listed in A015950.

a(87) > 10^14.

LINKS

Ryan Propper, Table of n, a(n) for n = 1..82, Feb 21 2007

Robert G. Wilson v, Table of n, a(n) for n = 1..10000 with -1 for those entries where a(n) has not yet been found

FORMULA

a(5^k-1) = 5^k.

MATHEMATICA

Do[k = 1; While[PowerMod[4, k, k] != n, k++ ]; Print[k], {n, 30}]

t = Table[0, {10000} ]; k = 1; While[ k < 5000000000, a = PowerMod[4, k, k]; If[a < 10001 && t[[a]] == 0, t[[a]] = k; Print[{a, k}]]; k++ ]; t

CROSSREFS

Cf. A015950, A036236, A078457, A119679, A127816, A119715, A119714, A127817, A127818, A127819, A127820, A127821.

Sequence in context: A268158 A050645 A048568 * A096682 A009215 A274078

Adjacent sequences:  A119675 A119676 A119677 * A119679 A119680 A119681

KEYWORD

nonn

AUTHOR

Ryan Propper, Jun 12 2006

EXTENSIONS

a(11) <= 2791496231, a(17) <= 140631956671, a(53) <= 52134328061 from Joe K. Crump (joecr(AT)carolina.rr.com), Feb 10 2007

a(11) = 2791496231 from Robert G. Wilson v, Feb 11 2007; confirmed by Ryan Propper, Feb 15 2007

Extended through n = 82 by Ryan Propper, Feb 21 2007

Search limits in the Mathematica coding is expanded by Robert G. Wilson v, Jul 14 2009

Link corrected by R. J. Mathar, Jul 24 2009

a(83) = 3085807457009 = 113 * 331 * 82501603 from Hagen von Eitzen, Jul 27 2009

STATUS

approved

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Last modified May 28 17:57 EDT 2017. Contains 287241 sequences.