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 A164007 Zero together with row 7 of the array in A163280. 5
 0, 13, 26, 33, 52, 55, 78, 91, 112, 135, 160, 187, 216, 247, 280, 315, 352, 391, 432, 475, 520, 567, 616, 667, 720, 775, 832, 891, 952, 1015, 1080, 1147, 1216, 1287, 1360, 1435, 1512, 1591, 1672, 1755, 1840, 1927, 2016, 2107, 2200, 2295, 2392, 2491, 2592, 2695 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS G. C. Greubel, Table of n, a(n) for n = 0..5000 Index entries for linear recurrences with constant coefficients, signature (3, -3, 1). FORMULA From G. C. Greubel, Aug 28 2017: (Start) a(n) = n*(n+6), n >= 7. a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3), n >= 7. G.f.: x*(13 - 13*x - 6*x^2 + 18*x^3 - 28*x^4 + 36*x^5 - 30*x^6 + 18*x^7 - 6*x^8))/(1 - x)^3. E.g.f.: (7*x + x^2)*exp(x) + 6*x +5*x^2 + x^3 + x^4/2 + x^6/120. MAPLE A033676 := proc(n) local a, d; a := 0 ; for d in numtheory[divisors](n) do if d^2 <= n then a := max(a, d) ; fi; od: a; end: A163280 := proc(n, k) local r, T ; r := 0 ; for T from k^2 by k do if A033676(T) = k then r := r+1 ; if r = n then RETURN(T) ; fi; fi; od: end: A164007 := proc(n) if n = 0 then 0; else A163280(7, n) ; fi; end: seq(A164007(n), n=0..80) ;  # R. J. Mathar, Aug 09 2009 MATHEMATICA Join[{0, 13, 26, 33, 52, 55, 78}, Table[n*(n + 6), {n, 7, 50}]] (* G. C. Greubel, Aug 28 2017 *) PROG (PARI) x='x+O('x^50); concat([0], Vec(x*(13 - 13*x - 6*x^2 + 18*x^3 - 28*x^4 + 36*x^5 - 30*x^6 + 18*x^7 - 6*x^8))/(1 - x)^3)) \\ G. C. Greubel, Aug 28 2017 CROSSREFS Cf. A008578, A161344, A161345, A163280, A164000, A164006, A164008. Cf. A028560 for n > 6. [R. J. Mathar, Aug 09 2009] Sequence in context: A037974 A318957 A180055 * A101870 A321714 A260748 Adjacent sequences:  A164004 A164005 A164006 * A164008 A164009 A164010 KEYWORD nonn AUTHOR Omar E. Pol, Aug 08 2009 EXTENSIONS Extended by R. J. Mathar, Aug 09 2009 STATUS approved

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Last modified June 16 06:46 EDT 2019. Contains 324145 sequences. (Running on oeis4.)