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 A007202 Crystal ball sequence for hexagonal close-packing. (Formerly M4899) 55
 1, 13, 57, 153, 323, 587, 967, 1483, 2157, 3009, 4061, 5333, 6847, 8623, 10683, 13047, 15737, 18773, 22177, 25969, 30171, 34803, 39887, 45443, 51493, 58057, 65157, 72813, 81047, 89879, 99331, 109423, 120177, 131613, 143753, 156617 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 REFERENCES N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS T. D. Noe, Table of n, a(n) for n = 0..1000 J. H. Conway and N. J. A. Sloane, Low-Dimensional Lattices VII: Coordination Sequences, Proc. Royal Soc. London, A453 (1997), 2369-2389 (pdf). Xiaogang Liang, Ilyar Hamid, and Haiming Duan, Dynamic stabilities of icosahedral-like clusters and their ability to form quasicrystals, AIP Advances 6, 065017 (2016). Index entries for linear recurrences with constant coefficients, signature (3,-2,-2,3,-1). FORMULA Nearest integer to (7/8)*( (n+1)^4 - n^4 ). G.f.: (x^4+10*x^3+20*x^2+10*x+1)/(x-1)^4/(x+1). a(n) = 7*(2*n+1)*(2*n^2+2*n+1)/8 +(-1)^n/8. - R. J. Mathar, Mar 24 2011 a(0)=1, a(1)=13, a(2)=57, a(3)=153, a(4)=323, a(n)=3*a(n-1)- 2*a(n-2)- 2*a(n-3)+3*a(n-4)-a(n-5). [Harvey P. Dale, Jul 15 2011] MATHEMATICA Table[Floor[(7((n+1)^4-n^4)+4)/8], {n, 0, 40}] (* or *) LinearRecurrence[ {3, -2, -2, 3, -1}, {1, 13, 57, 153, 323}, 40] (* Harvey P. Dale, Jul 15 2011 *) PROG (PARI) j=[]; for(n=0, 75, j=concat(j, round((7/8)*((n+1)^4-n^4)))); j (Python) def a(n): return round((7/8)*((n+1)**4-n**4)) print([a(n) for n in range(36)]) # Michael S. Branicky, Jan 13 2021 CROSSREFS Partial sums of A007899. The 28 uniform 3D tilings: cab: A299266, A299267; crs: A299268, A299269; fcu: A005901, A005902; fee: A299259, A299265; flu-e: A299272, A299273; fst: A299258, A299264; hal: A299274, A299275; hcp: A007899, A007202; hex: A005897, A005898; kag: A299256, A299262; lta: A008137, A299276; pcu: A005899, A001845; pcu-i: A299277, A299278; reo: A299279, A299280; reo-e:  A299281, A299282; rho: A008137, A299276; sod: A005893, A005894; sve: A299255, A299261; svh: A299283, A299284; svj: A299254, A299260; svk: A010001, A063489; tca: A299285, A299286; tcd: A299287, A299288; tfs: A005899, A001845; tsi: A299289, A299290; ttw: A299257, A299263; ubt: A299291, A299292; bnn: A007899, A007202. See the Proserpio link in A299266 for overview. Sequence in context: A212053 A264853 A210290 * A222161 A218593 A212405 Adjacent sequences:  A007199 A007200 A007201 * A007203 A007204 A007205 KEYWORD nonn,easy,nice,changed AUTHOR EXTENSIONS More terms from Jason Earls, Jul 14 2001 STATUS approved

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Last modified January 17 23:44 EST 2021. Contains 340249 sequences. (Running on oeis4.)