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A158131
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a(n) = 121*n + 1.
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2
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122, 243, 364, 485, 606, 727, 848, 969, 1090, 1211, 1332, 1453, 1574, 1695, 1816, 1937, 2058, 2179, 2300, 2421, 2542, 2663, 2784, 2905, 3026, 3147, 3268, 3389, 3510, 3631, 3752, 3873, 3994, 4115, 4236, 4357, 4478, 4599, 4720, 4841, 4962, 5083, 5204
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OFFSET
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1,1
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COMMENTS
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The identity (121*n+1)^2-(121*n^2+2*n)*(11)^2=1 can be written as a(n)^2-A181679(n)*(11)^2=1.
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LINKS
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FORMULA
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a(n) = 2*a(n-1)-a(n-2).
G.f.: x*(122-x)/(1-x)^2.
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MATHEMATICA
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LinearRecurrence[{2, -1}, {122, 243}, 50]
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PROG
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(Magma) I:=[122, 243]; [n le 2 select I[n] else 2*Self(n-1)-Self(n-2): n in [1..50]];
(PARI) a(n) = 121*n + 1.
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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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