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 A075921 Second column of triangle A075502. 2
 1, 21, 343, 5145, 74431, 1058841, 14941423, 210003465, 2945813311, 41281739961, 578226834703, 8097153012585, 113373983463391, 1587332657497881, 22223335428043183, 311131443554114505 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS The e.g.f. given below is Sum_{m=0..1} A075513(2,m)*exp(7*(m+1)*x). LINKS Index entries for linear recurrences with constant coefficients, signature (21, -98). FORMULA a(n) = A075502(n+2, 2) = (7^n)*S2(n+2, 2) with S2(n, m) := A008277(n, m) (Stirling2). a(n) = -7^n + 2*14^n. G.f.: 1/((1-7*x)*(1-14*x)). E.g.f.: (d^2/dx^2)(((exp(7*x)-1)/7)^2)/2! = -exp(7*x) + 2*exp(14*x). a(0)=1, a(1)=21, a(n) = 21a(n-1) - 98a(n-2). - Harvey P. Dale, Apr 30 2011 MATHEMATICA Table[-7^n+2 14^n, {n, 0, 20}] (* or *) LinearRecurrence[{21, -98}, {1, 21}, 20] (* Harvey P. Dale, Apr 30 2011 *) CROSSREFS Cf. A000420 (first column), A075922. Sequence in context: A144864 A295604 A323277 * A201878 A318269 A298229 Adjacent sequences:  A075918 A075919 A075920 * A075922 A075923 A075924 KEYWORD nonn,easy AUTHOR Wolfdieter Lang, Oct 02 2002 STATUS approved

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Last modified August 11 08:50 EDT 2020. Contains 336422 sequences. (Running on oeis4.)