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A004277 1 together with positive even numbers. 26
1, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, 100, 102, 104, 106, 108, 110, 112, 114, 116, 118, 120, 122, 124, 126, 128, 130, 132 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Also number of non-attacking bishops on n X n board. - Koksal Karakus (karakusk(AT)hotmail.com), May 27 2002

Engel expansion of e^(1/2) (see A006784 for definition) [when offset by 1] - Henry Bottomley, Dec 18 2000

Numbers n such that a 2n-group (i.e. a group of order 2n) has subgroup C_2. - Lekraj Beedassy, Oct 14 2004

Image of 1/(1-2x) under the mapping g(x)->g(x/(1+x^2)). - Paul Barry, Jan 16 2005

Position of n in A113322: A113322(a(n-1)) = n for n>0. - Reinhard Zumkeller, Oct 26 2005

Incrementally largest terms in the continued fraction for e. - Nick Hobson Jan 11 2007

Conjecturally, the differences of two consecutive primes (without repetition). [From Juri-Stepan Gerasimov, Nov 09 2009]

Equals (1, 2, 2, 2,...) convolved with (1, 0, 2, 0, 2, 0, 2,...). [From Gary W. Adamson, Mar 03 2010]

LINKS

Table of n, a(n) for n=0..66.

E. Friedman, Math. Magic

Index entries for sequences related to Engel expansions

FORMULA

G.f.: (1+x^2)/(1-x)^2 - Paul Barry, Feb 28 2003

Inverse binomial transform of Cullen numbers A002064. a(n)=2n+0^n. - Paul Barry, Jun 12 2003

a(n)=sum{k=0..floor(n/2), binomial(n-k-1)(-1)^k*2^(n-2k)}; - Paul Barry, Jan 16 2005

Equals binomial transform of [1, 1, 1, -1, 1, -1, 1,...]. - Gary W. Adamson, Jul 15 2008

E.g.f.: 1+x*sinh(x) (aerated sequence). [From Paul Barry, Oct 11 2009]

a(n) = 0^n + 2*n = A000007(n) + A005843(n). [Reinhard Zumkeller, Jan 11 2012]

MATHEMATICA

Join[{1}, Table[2*n, {n, 200}]] (* Vladimir Joseph Stephan Orlovsky, Jul 10 2011 *)

PROG

(Haskell)

a004277 n = 2 * n - 1 + signum (1 - n)

a004277_list = 0 : 1 : [2, 4 ..]  -- Reinhard Zumkeller, Dec 19 2013

CROSSREFS

Cf. A004275, A008486, A030978, A097134.

INVERT transformation yields A098182 without A098182(0). [From R. J. Mathar, Sep 11 2008]

Sequence in context: A119432 A005843 A076032 * A122080 A105360 A084564

Adjacent sequences:  A004274 A004275 A004276 * A004278 A004279 A004280

KEYWORD

easy,nonn

AUTHOR

N. J. A. Sloane.

EXTENSIONS

Corrected by Charles R Greathouse IV, Mar 18 2010

STATUS

approved

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Last modified September 2 14:44 EDT 2014. Contains 246361 sequences.