A249689 - OEIS

%I #17 Dec 13 2014 00:27:08

%S 16,65,91,1514,1993,1994,2452,2722,3047,3214,3931,3957,4356,4366,5191,

%T 5581,5805,5806,7519,8871,9228,9752,10036,10037,10039,10040,10963,

%U 10964,11278,11279,12015,12281,12595,12665,13262,13618,13648,15102,15103,18529,18991

%N Numbers n such that A084937(3n) > A084937(3n+1).

%H N. J. A. Sloane, <a href="/A249689/b249689.txt">Table of n, a(n) for n = 1..641</a> (Based on _John P. Linderman_'s computation of a million terms of A084937)

%o (AWK, using a-file for A084937)

%o awk ' BEGIN {s = 0}

%o       NR%3 == 0 { s = $2 }

%o       NR%3 == 1 { t = $2

%o           if (s > t)

%o              print( (NR-1)/3 )

%o         } ' a084937.txt | awk '{ print NR, $1}' >b249689.txt

%o (Python)

%o from __future__ import division

%o from fractions import gcd

%o A249689_list, l1, l2, s, b = [], 2, 1, 3, set()

%o for n in range(3,10**4):

%o ....i = s

%o ....while True:

%o ........if not i in b and gcd(i,l1) == 1 and gcd(i,l2) == 1:

%o ............l2, l1 = l1, i

%o ............b.add(i)

%o ............if l2 > l1 and n % 3 == 1:

%o ................A249689_list.append((n-1)//3)

%o ............while s in b:

%o ................b.remove(s)

%o ................s += 1

%o ............break

%o ........i += 1 # _Chai Wah Wu_, Dec 12 2014

%Y Cf. A084937

%K nonn

%O 1,1

%A _N. J. A. Sloane_, Nov 12 2014