This site is supported by donations to The OEIS Foundation.

 Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing. Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A287275 Number of set partitions of [n] such that for each block all absolute differences between consecutive elements are <= three. 4
 1, 1, 2, 5, 15, 47, 150, 481, 1545, 4965, 15958, 51293, 164871, 529947, 1703418, 5475329, 17599457, 56570281, 181834970, 584475733, 1878691887, 6038716423, 19410365422, 62391120801, 200545011401, 644615789581, 2072001259342, 6660074556205, 21407609138375 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS Alois P. Heinz, Table of n, a(n) for n = 0..1000 Pierpaolo Natalini, Paolo Emilio Ricci, New Bell-Sheffer Polynomial Sets, Axioms 2018, 7(4), 71. Wikipedia, Partition of a set Index entries for linear recurrences with constant coefficients, signature (4,-2,-2,1). FORMULA G.f.: -(x^3-3*x+1)/((x-1)*(x^3-x^2-3*x+1)). a(n) = A287214(n,3). a(n) = A000110(n) for n <= 4. EXAMPLE a(5) = 47 = 52 - 5 = A000110(5) - 5 counts all set partitions of [5] except: 15|234, 15|23|4, 15|24|3, 15|2|34, 15|2|3|4. CROSSREFS Column k=3 of A287214. Cf. A000110. Sequence in context: A143094 A308274 A058495 * A151280 A149914 A071735 Adjacent sequences:  A287272 A287273 A287274 * A287276 A287277 A287278 KEYWORD nonn,easy AUTHOR Alois P. Heinz, May 22 2017 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 December 14 14:59 EST 2019. Contains 329979 sequences. (Running on oeis4.)