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A087156 Nonnegative numbers excluding 1. 14
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
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 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
Sequence in context: A303502 A000027 A001477 * A254109 A317945 A292579
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 March 29 00:26 EDT 2024. Contains 371264 sequences. (Running on oeis4.)