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A080394 Numbers k such that binomial(k, floor(k/2)) is divisible by k^2. 3
1, 195, 273, 357, 385, 399, 585, 627, 665, 897, 935, 945, 957, 975, 1071, 1085, 1155, 1209, 1235, 1395, 1547, 1581, 1595, 1705, 1771, 1848, 1881, 1925, 1935, 1995, 2035, 2091, 2193, 2255, 2295, 2331, 2365, 2405, 2475, 2574, 2583, 2585, 2639, 2665, 2679 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
EXAMPLE
Very few values are even, like 1848 and 2574 (in A067348).
MATHEMATICA
Do[s=Binomial[n, Floor[n/2]]/n^2; If[IntegerQ[s], Print[n]], {n, 1, 10000}]
PROG
(PARI) is(k) = !(binomial(k, k\2) % n^2); \\ Amiram Eldar, Aug 11 2024
CROSSREFS
Cf. A073076.
Sequence in context: A234100 A336333 A351803 * A323975 A055970 A158225
KEYWORD
nonn
AUTHOR
Labos Elemer, Mar 18 2003
STATUS
approved

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Last modified September 6 06:40 EDT 2024. Contains 375704 sequences. (Running on oeis4.)