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 A098268 Unique prime factors of 2^n+1 are of the form kn+1. These are the values for k. 1
 2, 2, 0, 4, 2, 2, 6, 32, 2, 4, 62, 20, 210, 2, 8, 22, 4096, 2570, 2, 6, 9198, 3084, 258, 18, 96, 121574, 4, 28, 10, 162, 2, 6, 62, 3230, 563940, 2, 104592, 2, 44, 23091222 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The values for 2^n+1 are in A000051. In this sequence where a(n) has more than one k value they are separated with commas. See A097406 & A097407. LINKS PROG (PARI) isprimitivep(p, n) = {for (r=1, n-1, if (((2^r+1) % p) == 0, return (0)); ); return (1); } lista(n) = {f = factor(2^n+1); hasprim = 0; for(i=1, #f~, if (isprimitivep(f[i, 1], n), hasprim = 1; print1((f[i, 1]-1)/n, ", "); ); ); if (! hasprim, print1(0, ", ")); } \\ Michel Marcus, Jul 16 2013 CROSSREFS Sequence in context: A218875 A218869 A144458 * A330347 A329681 A276275 Adjacent sequences:  A098265 A098266 A098267 * A098269 A098270 A098271 KEYWORD nonn AUTHOR Marco Matosic, Sep 01 2004 STATUS approved

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Last modified September 24 06:13 EDT 2021. Contains 347623 sequences. (Running on oeis4.)