# Greetings from The On-Line Encyclopedia of Integer Sequences! http://oeis.org/ Search: id:a146330 Showing 1-1 of 1 %I A146330 #18 Mar 31 2020 03:03:51 %S A146330 41,149,157,181,269,397,425,493,565,697,761,941,1013,1037,1325,1565, %T A146330 1781,1825,2081,2153,2165,2173,2465,2477,2693,2725,3181,3221,3533, %U A146330 3869,4253,4409,5165,5213,5273,5297,5741,5837,6485,6757,6949,7045,7325,7465,8021,8069 %N A146330 Numbers k such that continued fraction of (1 + sqrt(k))/2 has period 5. %C A146330 For primes in this sequence see A146350. %H A146330 Amiram Eldar, Table of n, a(n) for n = 1..10000 %e A146330 a(1) = 41 because continued fraction of (1+sqrt(41))/2 = 3, 1, 2, 2, 1, 5, 1, 2, 2, 1, 5, 1, 2, 2, 1, 5, 1, 2, ... has period (1,2,2,1,5) length 5. %p A146330 isA146330 := proc(n) RETURN(A146326(n) = 5) ; end: %p A146330 for n from 2 to 2000 do if isA146330(n) then printf("%d,",n) ; fi; od: # _R. J. Mathar_, Sep 06 2009 %t A146330 Select[Range[10^4], !IntegerQ @ Sqrt[#] && Length[ContinuedFraction[(1 + Sqrt[#])/2][[2]]] == 5 &] (* _Amiram Eldar_, Mar 31 2020 *) %Y A146330 Cf. A000290, A078370, A146326-A146345, A146348-A146360. %K A146330 nonn %O A146330 1,1 %A A146330 _Artur Jasinski_, Oct 30 2008 %E A146330 259 and 1026 removed by _R. J. Mathar_, Sep 06 2009 %E A146330 More terms from _Amiram Eldar_, Mar 31 2020 # Content is available under The OEIS End-User License Agreement: http://oeis.org/LICENSE