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A074940 Numbers having at least one 2 in their ternary representation. 11
2, 5, 6, 7, 8, 11, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 29, 32, 33, 34, 35, 38, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 83, 86, 87, 88, 89, 92 (list; graph; refs; listen; history; internal format)
OFFSET

1,1

COMMENTS

Also, numbers n such that 3 divides C(2n,n).

Also, numbers n such that central trinomial coefficient A002426(n) == 0 (mod 3). - Emeric Deutsch and Bruce Sagan, Dec 04 2003

Also, numbers n such that A092255(n)==0 mod (3) - Benoit Cloitre (benoit7848c(AT)orange.fr), Mar 22 2004

Also, numbers n such that coefficient of x^n equals 0 in prod(k>=0, 1-x^(3^k))

LINKS

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

E. Deutsch and B. E. Sagan, Congruences for Catalan and Motzkin numbers and related sequences, J. Num. Theory 117 (2006), 191-215.

FORMULA

a(n) = n + O(n^0.631). [Charles R Greathouse IV, Aug 21 2011]

PROG

(PARI) is(n)=while(n, if(n%3==2, return(1)); n\=3); 0 \\ Charles R Greathouse IV, Aug 21 2011

(Haskell)

import Data.List (elemIndices)

a074940 n = a074940_list !! (n-1)

a074940_list = elemIndices 0 a039966_list

-- Reinhard Zumkeller, Sep 29 2011

CROSSREFS

Complement of A005836.

Cf. A006996, A007089, A081603, A081610, A081605, A081606.

A039966(a(n)) = 0.

Sequence in context: A122546 A028739 A170944 * A028752 A028791 A080727

Adjacent sequences:  A074937 A074938 A074939 * A074941 A074942 A074943

KEYWORD

easy,nonn

AUTHOR

Benoit Cloitre (benoit7848c(AT)orange.fr) and Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Oct 04 2002; revised Dec 03 2003

EXTENSIONS

More terms from Emeric Deutsch and Bruce Sagan, Dec 04 2003

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Last modified February 17 09:30 EST 2012. Contains 206009 sequences.