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A235536
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a(n) = binomial(8*n, 2*n) / (6*n + 1).
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3
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1, 4, 140, 7084, 420732, 27343888, 1882933364, 134993766600, 9969937491420, 753310723010608, 57956002331347120, 4524678117939182220, 357557785658996609700, 28545588568201512137904, 2298872717007844035521848, 186533392975795702301759056
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OFFSET
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0,2
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COMMENTS
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This is the case l=6, k=2 of binomial((l+k)*n,k*n)/((l*n+1)/gcd(k,l*n+1)), see Theorem 1.1 in Zhi-Wei Sun's paper.
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LINKS
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FORMULA
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G.f.: 6F5(1/8,1/4,3/8,5/8,3/4,7/8; 1/3,1/2,2/3,5/6,7/6; 65536*x/729).
a(n) ~ 2^(16*n-1)/(sqrt(Pi)*3^(6*n+3/2)*n^(3/2)). (End)
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MATHEMATICA
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Table[Binomial[8 n, 2 n]/(6 n + 1), {n, 0, 20}]
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PROG
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(Magma) l:=6; k:=2; [Binomial((l+k)*n, k*n)/(l*n+1): n in [0..20]]; /* where l is divisible by all the prime factors of k */
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CROSSREFS
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Cf. similar sequences generated by binomial((l+k)*n,k*n)/(l*n+1), where l is divisible by all the factors of k: A000108 (l=1, k=1), A001764 (l=2, k=1), A002293 (l=3, k=1), A002294 (l=4, k=1), A002295 (l=5, k=1), A002296 (l=6, k=1), A007556 (l=7, k=1), A062994 (l=8, k=1), A059968 (l=9, k=1), A230388 (l=10, k=1), A048990 (l=2, k=2), A235534 (l=4, k=2), this sequence (l=6, k=2), A187357 (l=3, k=3), A235535 (l=6, k=3).
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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