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 A340741 Numbers k such that A340740(k) is prime. 2
 7, 8, 9, 11, 12, 13, 15, 18, 19, 28, 31, 32, 34, 36, 44, 46, 47, 51, 52, 62, 64, 67, 69, 70, 73, 83, 88, 109, 110, 112, 128, 148, 153, 159, 189, 190, 192, 206, 212, 214, 222, 224, 226, 244, 245, 261, 267, 269, 280, 282, 283, 287, 300, 305, 312, 315, 319, 323, 366, 370, 378, 381, 388, 394, 404 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Robert Israel, Table of n, a(n) for n = 1..5000 EXAMPLE a(3) = 9 is a term because A340740(9) = 2 is prime. MAPLE f:= proc(n) local k; add(`if`(igcd(k, n)=1, n mod k, 0), k=1..floor(n/2)) end proc: select(t -> isprime(f(t)), [\$1..1000]); MATHEMATICA A340741[n_] := Position[Table[ PrimeQ[Sum[ Mod[m, i]*Floor[1/GCD[i, m]], {i, Floor[(m - 1)/2]}]], {m, 1, n}], True] // Flatten; A340741[404] (* Robert P. P. McKone, Jan 19 2021 *) PROG (PARI) isok(n) = isprime(sum(k=1, n\2, if (gcd(k, n)==1, n%k))); \\ Michel Marcus, Jan 18 2021 CROSSREFS Cf. A340731, A340740, A340742. Sequence in context: A035705 A205698 A210147 * A097338 A196040 A196043 Adjacent sequences: A340738 A340739 A340740 * A340742 A340743 A340744 KEYWORD nonn AUTHOR J. M. Bergot and Robert Israel, Jan 18 2021 STATUS approved

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Last modified April 18 09:35 EDT 2024. Contains 371779 sequences. (Running on oeis4.)