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URL: https://oeis.org/A280305

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A280305
a(n) = (n^(2n) - (n-1)^(2n))/(2n-1).
1
1, 5, 133, 8425, 968561, 175694701, 46142992981, 16549469742737, 7769425693383361, 4623280765312793221, 3400130923182845767301, 3028135414242749262553465, 3211431367839213404127361393, 3999028255132797763368898027805, 5777573340599982456777597457984981
OFFSET
1,2
COMMENTS
n such that a(n) is divisible by a square > 1: 4, 15, 22, 27, ...
LINKS
EXAMPLE
a(2) = 5 because (2^(2*2) - (2-1)^(2*2))/(2*2-1) = 5.
MATHEMATICA
Table[(n^(2n)-(n-1)^(2n))/(2n-1), {n, 20}] (* Harvey P. Dale, Nov 03 2025 *)
PROG
(Magma) [(n^(2*n) - (n-1)^(2*n))/(2*n-1): n in [1..15]];
CROSSREFS
Cf. A280302.
Sequence in context: A296191 A114474 A344395 * A085506 A307084 A132508
KEYWORD
nonn
AUTHOR
STATUS
approved