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A108696 Generated by a sieve: see comments. 4
1, 2, 3, 5, 7, 11, 13, 19, 23, 31, 35, 43, 49, 59, 61, 79, 83, 103, 109, 119, 133, 151, 155, 175, 193, 211, 215, 241, 259, 275, 283, 323, 331, 361, 373, 403, 419, 443, 455, 499, 511, 541, 571, 613, 623, 649, 673, 719, 733, 781, 803, 841, 871, 919 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Start with the natural numbers:

1 2 3 4 5 6 7 8 9 10 11 ...

Accept the 2nd number, 2 and erase every 2nd number after it, giving:

1 2 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 ...

Accept the 3rd number, 3 and erase every 3rd number after it, giving:

1 2 3 5 7 11 13 17 19 23 25 29 31 35 ...

Accept the 4th number, 5 and erase every 4th number after it, giving:

1 2 3 5 7 11 13 19 23 25 31 35 ...

Repeat!

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Index entries for sequences generated by sieves

PROG

(tcl) source /tclutils/utils.tcl

set l [range 0 10000]; set z z

for {set i 2} {$i*2 <= [llength $l]} {incr i} {

set k [expr {[llength $l]-1}]

set k [expr {$k - ($k % $i)}]

while {$k > $i} {

set l [lreplace $l $k $k]

incr k -$i

}

puts "after $i: length [llength $l], prefix [join [lrange $l 0 10] { }]"

}

(Haskell)

a108696 n = a108696_list !! (n-1)

a108696_list = 1 : sieve' 2 [2..] where

   sieve' n (x:xs) = x : (sieve' (n+1) $ sieving xs) where

      sieving xs = (take (n-1) xs) ++ (sieving $ drop n xs)

-- Reinhard Zumkeller, Jul 04 2011

CROSSREFS

Equals A007952 + 2 or equally A002491(n) + 1.

Sequence in context: A233893 A232824 A078334 * A215642 A092581 A130807

Adjacent sequences:  A108693 A108694 A108695 * A108697 A108698 A108699

KEYWORD

nonn

AUTHOR

David Applegate, Oct 11 2007

STATUS

approved

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Last modified April 14 03:53 EDT 2021. Contains 342941 sequences. (Running on oeis4.)