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A324265
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a(n) = 5*343^n.
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1
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5, 1715, 588245, 201768035, 69206436005, 23737807549715, 8142067989552245, 2792729320416420035, 957906156902832072005, 328561811817671400697715, 112696701453461290439316245, 38654968598537222620685472035, 13258654229298267358895116908005, 4547718400649305704101025099445715
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OFFSET
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0,1
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COMMENTS
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x = a(n) and y = A324266(n) satisfy the Lebesgue-Ramanujan-Nagell equation x^2 + 7^(6*n+1) = 4*y^3 (see Theorem 2.1 in Chakraborty, Hoque and Sharma).
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LINKS
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FORMULA
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O.g.f.: 5/(1 - 343*x).
E.g.f.: 5*exp(343*x).
a(n) = 343*a(n-1) for n > 0.
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EXAMPLE
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For a(0) = 5 and A324266(0) = 2, 5^2 + 7 = 32 = 4*2^3.
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MAPLE
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a:=n->5*343^n: seq(a(n), n=0..20);
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MATHEMATICA
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5*343^Range[0, 20]
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PROG
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(GAP) List([0..20], n->5*343^n);
(Magma) [5*343^n: n in [0..20]];
(PARI) a(n) = 5*343^n;
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CROSSREFS
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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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