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A066246 0 unless n is a composite number A002808(k) when a(n) = k. 16
0, 0, 0, 1, 0, 2, 0, 3, 4, 5, 0, 6, 0, 7, 8, 9, 0, 10, 0, 11, 12, 13, 0, 14, 15, 16, 17, 18, 0, 19, 0, 20, 21, 22, 23, 24, 0, 25, 26, 27, 0, 28, 0, 29, 30, 31, 0, 32, 33, 34, 35, 36, 0, 37, 38, 39, 40, 41, 0, 42, 0, 43, 44, 45, 46, 47, 0, 48, 49, 50, 0, 51, 0, 52, 53, 54, 55, 56, 0, 57 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,6

COMMENTS

a(n) = A239968(n) + A010051(n) - 1. - Reinhard Zumkeller, Mar 30 2014

LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

PROG

(PARI) a(n)=if(isprime(n), 0, max(0, n-primepi(n)-1)) \\ Charles R Greathouse IV, Aug 21 2011

(Haskell)

import Data.List (unfoldr, genericIndex)

a066246 n = genericIndex a066246_list (n - 1)

a066246_list = unfoldr x (1, 1, a002808_list) where

   x (i, z, cs'@(c:cs)) | i == c = Just (z, (i + 1, z + 1, cs))

                        | i /= c = Just (0, (i + 1, z, cs'))

-- Reinhard Zumkeller, Jan 29 2014

CROSSREFS

Cf. A049084.

Cf. A026233, A026238.

Sequence in context: A137218 A087819 A278029 * A198370 A173517 A109921

Adjacent sequences:  A066243 A066244 A066245 * A066247 A066248 A066249

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Dec 09 2001

STATUS

approved

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Last modified February 22 18:16 EST 2018. Contains 299469 sequences. (Running on oeis4.)