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 A087156 Nonnegative numbers excluding 1. 13
 0, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS The old entry with this sequence number was a duplicate of A026835. A063524(a(n)) = 0. - Reinhard Zumkeller, Oct 11 2008 Inverse binomial transform of A006589. - Philippe Deléham, Nov 25 2008 a(n) = maximum value of j, where 1 <= j <= n-1, such that floor(j^2 / n) > 0 for each n. LINKS Index entries for linear recurrences with constant coefficients, signature (2,-1). FORMULA G.f.: x^2*(2-x)/(1-x)^2 . E.g.f.: x*(exp(x)-1). - Philippe Deléham, Nov 25 2008 a(n) = A163300(n)/2. - Juri-Stepan Gerasimov, Aug 14 2009 a(n) = n-1+[(n+1) mod n], with n>=1. - Paolo P. Lava, Nov 06 2009 a(n) = n mod sigma_k(n), where sigma_k is the k divisor sigma function. -Enrique Pérez Herrero, Nov 11 2009 a(n+1) = floor((n+sqrt(n^2+8n))/2). - Philippe Deléham, Oct 03 2011 a(n) = n mod n^2. - Andrew Secunda, Aug 21 2015 MATHEMATICA A087156[n_] := Mod[n, DivisorSigma[1, n]] (* Enrique Pérez Herrero, Nov 11 2009 *) Drop[Range[0, 80], {2}] (* Harvey P. Dale, Dec 13 2011 *) PROG (PARI) a(n)=n-(n==1) \\ Charles R Greathouse IV, Aug 26 2011 (MAGMA) [n mod n^2: n in [1..100]]; // Vincenzo Librandi, Aug 22 2015 CROSSREFS Cf. A000027, A166373. Sequence in context: A303502 A000027 A001477 * A254109 A317945 A292579 Adjacent sequences:  A087153 A087154 A087155 * A087157 A087158 A087159 KEYWORD nonn,easy AUTHOR N. J. A. Sloane, Oct 11 2008 EXTENSIONS Comment and cross-reference added by Christopher Hunt Gribble, Oct 14 2009, Oct 17 2009 STATUS approved

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Last modified September 21 17:46 EDT 2019. Contains 327273 sequences. (Running on oeis4.)