A146330 - OEIS

A146330

Numbers k such that continued fraction of (1 + sqrt(k))/2 has period 5.

41, 149, 157, 181, 269, 397, 425, 493, 565, 697, 761, 941, 1013, 1037, 1325, 1565, 1781, 1825, 2081, 2153, 2165, 2173, 2465, 2477, 2693, 2725, 3181, 3221, 3533, 3869, 4253, 4409, 5165, 5213, 5273, 5297, 5741, 5837, 6485, 6757, 6949, 7045, 7325, 7465, 8021, 8069

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

For primes in this sequence see A146350.

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000

EXAMPLE

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.

MAPLE

isA146330 := proc(n) RETURN(A146326(n) = 5) ; end:

for n from 2 to 2000 do if isA146330(n) then printf("%d, ", n) ; fi; od: # R. J. Mathar, Sep 06 2009