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 A004277 1 together with positive even numbers. 40
 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). - Juri-Stepan Gerasimov, Nov 09 2009 Equals (1, 2, 2, 2, ...) convolved with (1, 0, 2, 0, 2, 0, 2, ...). - Gary W. Adamson, Mar 03 2010 a(n) is the number of 0-dimensional elements (vertices) in an n-cross polytope. - Patrick J. McNab, Jul 06 2015 Numbers k such that in the symmetric representation of sigma(k) there is no pair bars as its ends (Cf. A237593). - Omar E. Pol, Sep 28 2018 Also, the coordination sequence of the L-lattice (see A332419). - Sean A. Irvine, Jul 29 2020 LINKS Table of n, a(n) for n=0..66. E. Friedman, Math. Magic Eric Weisstein's World of Mathematics, Cross Polytope Index entries for sequences related to Engel expansions Index entries for linear recurrences with constant coefficients, signature (2, -1). 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). - 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 *) Select[Range@ 105, PowerMod[#, #, # + 1] == 1 &] (* Robert G. Wilson v, Sep 26 2016 *) PROG (Haskell) a004277 n = 2 * n - 1 + signum (1 - n) a004277_list = 1 : [2, 4 ..] -- Reinhard Zumkeller, Dec 19 2013 (Magma)  cat [2*n: n in [1..80]]; // Vincenzo Librandi, Jul 11 2015 CROSSREFS Cf. A004275, A008486, A030978, A097134. INVERT transformation yields A098182 without A098182(0). - R. J. Mathar, Sep 11 2008 Sequence in context: A317108 A317440 A076032 * A299174 A122080 A105360 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 24 13:22 EDT 2023. Contains 365579 sequences. (Running on oeis4.)