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 A170790 a(n) = n^9*(n^8 + 1)/2. 2
 0, 1, 65792, 64579923, 8590065664, 381470703125, 8463334761216, 116315277170407, 1125899973951488, 8338591043543529, 50000000500000000, 252723515428620731, 1109305555950108672, 4325207964992918653 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS Number of unoriented rows of length 17 using up to n colors. For a(0)=0, there are no rows using no colors. For a(1)=1, there is one row using that one color for all positions. For a(2)=65792, there are 2^17=131072 oriented arrangements of two colors. Of these, 2^9=512 are achiral. That leaves (131072-512)/2=65280 chiral pairs. Adding achiral and chiral, we get 65792. - Robert A. Russell, Nov 13 2018 LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..10000 Index entries for linear recurrences with constant coefficients, signature (18,-153,816,-3060,8568,-18564, 31824,-43758,48620,-43758,31824,-18564,8568,-3060,816,-153,18,-1). FORMULA G.f.: (x + 65774*x^2 + 63395820*x^3 + 7437692410*x^4 + 236676566180*x^5 + 2858646249342*x^6 + 15527826341908*x^7 + 41568611082650*x^8 + 57445191259830*x^9 + 41568611082650*x^10 + 15527826341908*x^11 + 2858646249342*x^12 + 236676566180*x^13 + 7437692410*x^14 + 63395820*x^15 + 65774*x^16 + x^17)/(1-x)^18. - G. C. Greubel, Dec 06 2017 From Robert A. Russell, Nov 13 2018: (Start) a(n) = (A010805(n) + A001017(n)) / 2 = (n^17 + n^9) / 2. G.f.: (Sum_{j=1..17} S2(17,j)*j!*x^j/(1-x)^(j+1) + Sum_{j=1..9} S2(9,j)*j!*x^j/(1-x)^(j+1)) / 2, where S2 is the Stirling subset number A008277. G.f.: x*Sum_{k=0..16} A145882(17,k) * x^k / (1-x)^18. E.g.f.: (Sum_{k=1..17} S2(17,k)*x^k + Sum_{k=1..9} S2(9,k)*x^k) * exp(x) / 2, where S2 is the Stirling subset number A008277. For n>17, a(n) = Sum_{j=1..18} -binomial(j-19,j) * a(n-j). (End) MATHEMATICA Table[(n^9 (n^8+1))/2, {n, 0, 20}] (* Harvey P. Dale, Oct 03 2016 *) PROG (Magma) [n^9*(n^8+1)/2: n in [0..20]]; // Vincenzo Librandi, Aug 26 2011 (PARI) for(n=0, 30, print1(n^9*(n^8+1)/2, ", ")) \\ G. C. Greubel, Dec 06 2017 (Sage) [n^9*(n^8+1)/2 for n in range(30)] # G. C. Greubel, Nov 15 2018 (GAP) List([0..30], n -> n^9*(n^8+1)/2); # G. C. Greubel, Nov 15 2018 (Python) for n in range(0, 20): print(int(n**9*(n**8 + 1)/2), end=', ') # Stefano Spezia, Nov 15 2018 CROSSREFS Row 17 of A277504. Cf. A010805 (oriented), A001017 (achiral). Sequence in context: A170781 A063825 A253043 * A043678 A032781 A170799 Adjacent sequences: A170787 A170788 A170789 * A170791 A170792 A170793 KEYWORD nonn,easy AUTHOR N. J. A. Sloane, Dec 11 2009 STATUS approved

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Last modified July 14 13:51 EDT 2024. Contains 374318 sequences. (Running on oeis4.)