This site is supported by donations to The OEIS Foundation.

 Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing. Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A126881 a(1)=1, a(2)=2. a(n) is the a(n-1)th integer from among those positive integers coprime to a(n-2). 1
 1, 2, 2, 3, 5, 7, 8, 9, 17, 25, 26, 32, 69, 137, 214, 215, 433, 553, 554, 654, 1311, 3967, 6565, 6566, 8979, 21267, 33151, 53216, 53217, 106497, 161963, 242965, 244832, 306046, 714759, 1579093, 2396450, 2420102, 7278679, 14557369, 14778071 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS EXAMPLE a(4)=3, a(5)=5. So a(6) is the 5th positive integer which is coprime to 3. 3 is coprime to 1,2,4,5,7,8,10,11,... So a(6) is the 5th of these, which is 7. MATHEMATICA f[m_, n_] := Block[{k = 0, c = n}, While[c > 0, k++; While[GCD[k, m] > 1, k++ ]; c--; ]; k]; g[l_] := Append[l, f[l[[ -2]], l[[ -1]]]]; Nest[g, {1, 2}, 40] (* Ray Chandler, Dec 31 2006 *) CROSSREFS Cf. A126882. Sequence in context: A178880 A079953 A133393 * A290273 A125505 A061565 Adjacent sequences:  A126878 A126879 A126880 * A126882 A126883 A126884 KEYWORD nonn AUTHOR Leroy Quet, Dec 29 2006 EXTENSIONS Extended by Ray Chandler, Dec 31 2006 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified December 5 13:26 EST 2019. Contains 329751 sequences. (Running on oeis4.)