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 A224808 Number of permutations (p(1), p(2), ..., p(n)) satisfying -k <= p(i)-i <= r and p(i)-i not in the set I, i=1..n, with k=2, r=6, I={-1,1,2,3,4,5}. 8
 1, 1, 1, 1, 1, 1, 1, 2, 4, 6, 9, 12, 16, 20, 25, 35, 49, 70, 100, 140, 196, 266, 361, 494, 676, 936, 1296, 1800, 2500, 3450, 4761, 6555, 9025, 12445, 17161, 23711, 32761, 45250, 62500, 86250, 119025, 164220, 226576, 312732, 431649, 595899, 822649, 1135564, 1567504, 2163456, 2985984 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,8 COMMENTS a(n) is the number of subsets of {1,2,...,n-6} without differences equal to 2, 4 or 6. LINKS G. C. Greubel, Table of n, a(n) for n = 0..1000 Vladimir Baltic, On the number of certain types of strongly restricted permutations, Applicable Analysis and Discrete Mathematics Vol. 4, No 1 (April, 2010), 119-135 Index entries for linear recurrences with constant coefficients, signature (1,0,0,0,1,-1,1,2,-1,1,0,0,-1,0,0, 1). FORMULA a(n) = a(n-1) + a(n-5) - a(n-6) + a(n-7) + 2*a(n-8) - a(n-9) + a(n-10) - a(n-13) + a(n-16). G.f.: (1-x^5-x^8)/(1-x-x^5+x^6-x^7-2*x^8+x^9-x^10+x^13+x^16). a(2*k-2) = (A003269(k))^2, a(2*k-1) = A003269(k) * A003269(k+1) MATHEMATICA CoefficientList[Series[(1 - x^5 - x^8)/(1 - x - x^5 + x^6 - x^7 - 2*x^8 + x^9 - x^10 + x^13 + x^16), {x, 0, 50}], x] (* G. C. Greubel, Oct 28 2017 *) PROG (PARI) x='x+O('x^66); Vec((1-x^5-x^8)/(1-x-x^5+x^6-x^7-2*x^8+x^9-x^10+x^13+x^16) ) \\ Joerg Arndt, Apr 19 2013 CROSSREFS Cf. A002524-A002529, A072827, A072850-A072856, A079955-A080014, A217694. Sequence in context: A024617 A025698 A194211 * A292459 A194250 A024610 Adjacent sequences:  A224805 A224806 A224807 * A224809 A224810 A224811 KEYWORD nonn AUTHOR Vladimir Baltic, Apr 18 2013 STATUS approved

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Last modified May 9 12:19 EDT 2021. Contains 343740 sequences. (Running on oeis4.)