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 A240661 Least k such that 6^k == -1 (mod prime(n)), or 0 if no such k exists. 1
 0, 0, 0, 1, 5, 6, 8, 0, 0, 7, 3, 2, 20, 0, 0, 13, 29, 30, 0, 0, 18, 39, 41, 44, 6, 5, 51, 53, 54, 56, 63, 65, 68, 0, 0, 75, 78, 0, 0, 0, 89, 30, 0, 48, 7, 99, 0, 111, 113, 114, 116, 0, 10, 125, 128, 0, 67, 135, 138, 28, 0, 73, 0, 0, 26, 79, 0, 28, 173, 58, 16 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,5 COMMENTS The least k, if it exists, such that prime(n) divides 6^k + 1. LINKS T. D. Noe, Table of n, a(n) for n = 1..1000 FORMULA a(n) = A211242(n)/2 if A211242(n) is even, otherwise 0. MATHEMATICA Table[p = Prime[n]; s = Select[Range[p/2], PowerMod[6, #, p] == p - 1 &, 1]; If[s == {}, 0, s[[1]]], {n, 100}] CROSSREFS Cf. A211242 (order of 6 mod prime(n)). Sequence in context: A048090 A048027 A294071 * A153430 A329089 A100379 Adjacent sequences: A240658 A240659 A240660 * A240662 A240663 A240664 KEYWORD nonn AUTHOR T. D. Noe, Apr 14 2014 STATUS approved

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Last modified December 5 20:27 EST 2023. Contains 367594 sequences. (Running on oeis4.)