OFFSET
1,1
COMMENTS
Sequence appears to include all numbers m such that 8^5 is the highest power of 2 dividing A005148(m). General conjecture: numbers k such that 8^j is the highest power of 2 dividing A005148(k) is the same sequence as numbers having exactly (j+1) 1's in their binary representation. - Benoit Cloitre, Jun 22 2002
LINKS
Ivan Neretin, Table of n, a(n) for n = 1..10000
Robert Baillie, Summing the curious series of Kempner and Irwin, arXiv:0806.4410 [math.CA], 2008-2015. See p. 18 for Mathematica code irwinSums.m.
FORMULA
a(n+1) = A057168(a(n)). - M. F. Hasler, Aug 27 2014
Sum_{n>=1} 1/a(n) = 1.387753111935705074750004158584017188750706394077047633137401652680870607884... (calculated using Baillie's irwinSums.m, see Links). - Amiram Eldar, Feb 14 2022
MATHEMATICA
Select[ Range[ 63, 380 ], (Count[ IntegerDigits[ #, 2 ], 1 ]==6)& ]
PROG
(PARI) is_A023688(n)=hammingweight(n)==6 \\ M. F. Hasler, Aug 27 2014
(PARI) print1(t=2^6-1); for(i=2, 50, print1(", "t=A057168(t))) \\ M. F. Hasler, Aug 27 2014
(Python)
from itertools import islice
def A023688_gen(): # generator of terms
yield (n:=63)
while True: yield (n:=((n&~(b:=n+(a:=n&-n)))>>a.bit_length())^b)
CROSSREFS
KEYWORD
nonn,base,easy,changed
AUTHOR
STATUS
approved