A098268 Unique prime factors of 2^n+1 are of the form kn+1. These are the values for k.

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

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

Table of n, a(n) for n=1..40.

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