This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A047355 Numbers that are congruent to {0, 3} mod 7. 13
 0, 3, 7, 10, 14, 17, 21, 24, 28, 31, 35, 38, 42, 45, 49, 52, 56, 59, 63, 66, 70, 73, 77, 80, 84, 87, 91, 94, 98, 101, 105, 108, 112, 115, 119, 122, 126, 129, 133, 136, 140, 143, 147, 150, 154, 157, 161, 164, 168, 171, 175, 178, 182, 185, 189, 192, 196, 199, 203 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Numbers k such that k^2/7 + k*(k + 1)/7 = k*(2*k + 1)/7 is a nonnegative integer. - Bruno Berselli, Feb 14 2017 LINKS Index entries for linear recurrences with constant coefficients, signature (1,1,-1). FORMULA a(n) = a(n-2) + 7 = a(n-1) + a(n-2) - a(n-3). - Henry Bottomley, Jan 19 2001 a(n) = 7*n - a(n-1) - 11 for n>1, a(1)=0. - Vincenzo Librandi, Aug 05 2010 From Bruno Berselli, Sep 12 2011: (Start) G.f.: x^2*(3 + 4*x)/((1 + x)*(1 - x)^2). a(n) = (14*n - (-1)^n - 15)/4. (End) a(n+1) = sum_{k>=0} {A030308(n,k)*A125176(k+2)}. - Philippe Deléham, Oct 17 2011. a(n) = 2*n - 2 + floor((3*n - 3)/2). - Wesley Ivan Hurt, Jan 30 2014 MAPLE A047355:=n->(14*n - (-1)^n - 15)/4; seq(A047355(n), n=1..100); # Wesley Ivan Hurt, Jan 30 2014 MATHEMATICA Table[(14n - (-1)^n - 15)/4, {n, 100}] (* Wesley Ivan Hurt, Jan 30 2014 *) PROG (Haskell) a047355 n = a047355_list !! (n-1) a047355_list = scanl (+) 0 a010702_list -- Reinhard Zumkeller, Jul 05 2012 (PARI) a(n)=n\2*7 - 4 + n%2*4 \\ Charles R Greathouse IV, Aug 01 2016 CROSSREFS Cf. A030123, A010702 (first differences). Sequence in context: A288999 A310187 A198268 * A248522 A098005 A322533 Adjacent sequences:  A047352 A047353 A047354 * A047356 A047357 A047358 KEYWORD nonn,easy AUTHOR STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified August 19 18:51 EDT 2019. Contains 326133 sequences. (Running on oeis4.)