

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
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OFFSET

0,2


COMMENTS

Also number of nonattacking 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 2ngroup (i.e. a group of order 2n) has subgroup C_2.  Lekraj Beedassy, Oct 14 2004
Image of 1/(12x) under the mapping g(x)>g(x/(1+x^2)).  Paul Barry, Jan 16 2005
Position of n in A113322: A113322(a(n1)) = 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 JuriStepan 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)/(1x)^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(nk1)(1)^k*2^(n2k)};  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



