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A349074
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a(n) = U(3*n, n), where U(n, x) is the Chebyshev polynomial of the second kind.
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5
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1, 4, 2911, 7997214, 57641556673, 867583274883920, 23630375698358890319, 1056918444955456528983706, 72383076947075470731692782081, 7200266529428094485775774835670652, 998383804974887102441600687728515247999, 186701261436825568741051032736345268517903734
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OFFSET
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0,2
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COMMENTS
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In general, for k>=1, U(k*n, n) ~ 2^(k*n) * n^(k*n).
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LINKS
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FORMULA
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For n>1, a(n) = ((n + sqrt(n^2-1))^(3*n+1) - (n - sqrt(n^2-1))^(3*n+1)) / (2*sqrt(n^2-1)).
a(n) ~ 2^(3*n) * n^(3*n).
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MATHEMATICA
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Table[ChebyshevU[3*n, n], {n, 0, 13}]
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PROG
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(PARI) a(n) = polchebyshev(3*n, 2, n); \\ Michel Marcus, Nov 07 2021
(Python)
from sympy import chebyshevu
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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