This site is supported by donations to The OEIS Foundation. Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A268368 An eventually quasi-quadratic sequence satisfying a Hofstadter-like recurrence. 7
 0, 1, 0, 4, 4, 4, 3, 12, 8, 4, 3, 24, 12, 4, 3, 40, 16, 4, 3, 60, 20, 4, 3, 84, 24, 4, 3, 112, 28, 4, 3, 144, 32, 4, 3, 180, 36, 4, 3, 220, 40, 4, 3, 264, 44, 4, 3, 312, 48, 4, 3, 364, 52, 4, 3, 420, 56, 4, 3, 480, 60, 4, 3, 544, 64, 4, 3, 612, 68, 4, 3, 684 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,4 COMMENTS a(n) is the solution to the recurrence relation a(n) = a(n-a(n-1)) + a(n-a(n-2)) + a(n-a(n-3)), with the initial conditions: a(n) = 0 if n <= 0; a(1) = 0, a(2) = 1, a(3) = 0, a(4) = 4, a(5) = 4, a(6) = 4, a(7) = 3. LINKS Colin Barker, Table of n, a(n) for n = 1..1000 Index entries for linear recurrences with constant coefficients, signature (0,0,0,3,0,0,0,-3,0,0,0,1). FORMULA a(2) = 1, a(3) = 0; otherwise a(4n) = 2n^2+2n, a(4n+1) = 4n, a(4n+2) = 4, a(4n+3) = 3. From Colin Barker, Jun 22 2017: (Start) G.f.: x^2*(1 + 4*x^2 + 4*x^3 + x^4 + 3*x^5 - 4*x^7 - 5*x^8 - 6*x^9 + 3*x^12 + 3*x^13) / ((1 - x)^3*(1 + x)^3*(1 + x^2)^3). a(n) = 3*a(n-4) - 3*a(n-8) + a(n-12) for n>12. (End) PROG (PARI) concat(0, Vec(x^2*(1 + 4*x^2 + 4*x^3 + x^4 + 3*x^5 - 4*x^7 - 5*x^8 - 6*x^9 + 3*x^12 + 3*x^13) / ((1 - x)^3*(1 + x)^3*(1 + x^2)^3) + O(x^100))) \\ Colin Barker, Jun 22 2017 CROSSREFS Cf. A005185, A188670, A244477, A264757, A267501. Sequence in context: A073259 A174987 A214926 * A274947 A279406 A171408 Adjacent sequences:  A268365 A268366 A268367 * A268369 A268370 A268371 KEYWORD nonn,easy AUTHOR Nathan Fox, Feb 23 2016 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 October 13 18:14 EDT 2019. Contains 327981 sequences. (Running on oeis4.)