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A127817 a(n) = least k such that the remainder when 9^k is divided by k is n. 46
2, 7, 6, 5, 38, 723, 74, 2592842671511, 11, 3827, 14, 717, 34, 59035, 21, 259, 152, 237, 62, 626131, 30, 169, 58, 25, 56, 1921, 39, 361, 65, 49, 63010, 287, 48, 55, 46, 63, 932, 3786791, 69, 69637, 230, 221, 6707, 1057, 57, 4907, 253, 681, 148, 393217991, 70 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..51.

Fausto A. C. Cariboni, Table of n, a(n) for n = 1..10000 with -1 for large entries where a(n) has not yet been found, Nov 21 2016 [With 202 new terms, this supersedes an earlier table of Robert G. Wilson v et al.]

EXAMPLE

For n=4, since 9^5 == 4 (mod 5) and 9^k is not congruent to 4 (mod k) for any k < 5, a(4) = 5. Michael B. Porter, Dec 10 2016

MAPLE

a127817 := [seq(0, j=1..nmax)] ; for k from 1 do n := modp(9^k, k) ; if n > 0 and n <= nmax then if op(n, a127817) = 0 then a127817 := subsop(n=k, a127817) ; print( op(1..50, a127817) ) ; fi; fi; od: # R. J. Mathar, Jul 16 2009

MATHEMATICA

t = Table[0, {10000}]; k = 1; lst = {}; While[k < 4500000000, a = PowerMod[9, k, k]; If[ a<10001 && t[[a]]==0, t[[a]]=k; Print[{a, k}]]; k++ ]; t

CROSSREFS

Cf. A036236, A078457, A119678, A119679, A127816, A119715, A119714, A127818, A127819, A127820, A127821.

Sequence in context: A074067 A110988 A047224 * A199173 A047232 A103557

Adjacent sequences:  A127814 A127815 A127816 * A127818 A127819 A127820

KEYWORD

hard,nonn

AUTHOR

Alexander Adamchuk, Jan 30 2007

EXTENSIONS

a(8) <= 2592842671511 from Joe K. Crump (joecr(AT)carolina.rr.com), Feb 06 2007

I changed the Mathematica coding to reflect the current limits Robert G. Wilson v, Jul 18 2009

Value for a(8) as suggested by J. K. Crump confirmed by Hagen von Eitzen, Jul 21 2009

Authorship of a-file corrected by R. J. Mathar, Aug 24 2009

STATUS

approved

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Last modified May 26 18:58 EDT 2017. Contains 287129 sequences.