The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Please make a donation to keep the OEIS running. We are now in our 56th year. In the past year we added 10000 new sequences and reached almost 9000 citations (which often say "discovered thanks to the OEIS"). Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A286225 Number of compositions (ordered partitions) of n into parts with an even number of distinct prime divisors. 3
 1, 1, 1, 1, 1, 1, 2, 3, 4, 5, 7, 9, 13, 18, 25, 34, 46, 61, 83, 112, 153, 209, 286, 387, 526, 713, 969, 1317, 1794, 2437, 3312, 4497, 6110, 8302, 11290, 15347, 20865, 28354, 38533, 52361, 71167, 96721, 131464, 178672, 242834, 330020, 448532, 609590, 828511, 1126037, 1530418, 2079977, 2826896, 3841998 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,7 LINKS Amiram Eldar, Table of n, a(n) for n = 0..7000 Eric Weisstein's World of Mathematics, Distinct Prime Factors FORMULA G.f.: 1/(1 - Sum_{k>=1} x^A030231(k)). EXAMPLE a(8) = 4 because we have [6, 1, 1], [1, 6, 1], [1, 1, 6] and [1, 1, 1, 1, 1, 1, 1, 1]. MATHEMATICA nmax = 53; CoefficientList[Series[1/(1 - Sum[Boole[EvenQ[PrimeNu[k]]] x^k, {k, 1, nmax}]), {x, 0, nmax}], x] CROSSREFS Cf. A030231, A285798, A286221, A286224. Sequence in context: A320316 A236166 A017834 * A239048 A219898 A263360 Adjacent sequences:  A286222 A286223 A286224 * A286226 A286227 A286228 KEYWORD nonn AUTHOR Ilya Gutkovskiy, May 04 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 November 29 01:03 EST 2020. Contains 338755 sequences. (Running on oeis4.)