A249689 Numbers k such that A084937(3k) > A084937(3k+1).

16, 65, 91, 1514, 1993, 1994, 2452, 2722, 3047, 3214, 3931, 3957, 4356, 4366, 5191, 5581, 5805, 5806, 7519, 8871, 9228, 9752, 10036, 10037, 10039, 10040, 10963, 10964, 11278, 11279, 12015, 12281, 12595, 12665, 13262, 13618, 13648, 15102, 15103, 18529, 18991

Offset: 1

Author

N. J. A. Sloane, Nov 12 2014

Keywords

• nonn

Links

• N. J. A. Sloane, Table of n, a(n) for n = 1..641 (Based on _John P. Linderman_'s computation of a million terms of A084937)

Crossrefs

Cf. A084937

Programs

AWK

# Using a-file for A084937.
awk ' BEGIN {s = 0}
      NR%3 == 0 { s = $2 }
      NR%3 == 1 { t = $2
          if (s > t)
             print( (NR-1)/3 )
        } ' a084937.txt | awk '{ print NR, $1}' >b249689.txt

Python

from math import gcd
A249689_list, l1, l2, s, b = [], 2, 1, 3, set()
for n in range(3,10**4):
    i = s
    while True:
        if not i in b and gcd(i,l1) == 1 and gcd(i,l2) == 1:
            l2, l1 = l1, i
            b.add(i)
            if l2 > l1 and n % 3 == 1:
                A249689_list.append((n-1)//3)
            while s in b:
                b.remove(s)
                s += 1
            break
        i += 1 # Chai Wah Wu, Dec 12 2014