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A290583 a(n) is the factor R(n) having prime factors < (2/3)*n^2 in A285388(n) = R(n)P(n). 1
1, 1, 15, 45, 28665, 119301, 5945469075, 349882586625, 37442407704398235, 16728192398775, 15367416005321626675, 25155676359358573576275, 8796919422969373203777212374275, 276042834397113472381083873409429425 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Prime factors > sqrt(2)*n occur with multiplicity 1.

LINKS

Table of n, a(n) for n=1..14.

FORMULA

a(n) = A285388(n)/A290584(n).

EXAMPLE

a(4)=45: A285388(4) = 300540195 = (R(4) = 3*3*5 = 45)*(P(4) = 6678671).

PROG

(PARI) a285388(n) = my(m=n*binomial(2*n^2, n^2)); m>>valuation(m, 2);

a(n) = my(f=factor(a285388(n))); for (k=1, #f~, if (f[k, 1] >= (2/3)*n^2, f[k, 1] = 1)); factorback(f); \\ Michel Marcus, Aug 07 2017

CROSSREFS

Cf. A285388, A290584 (P(n)).

Sequence in context: A219813 A068513 A267079 * A033480 A041434 A136430

Adjacent sequences:  A290580 A290581 A290582 * A290584 A290585 A290586

KEYWORD

nonn

AUTHOR

Ralf Steiner, Aug 07 2017

STATUS

approved

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Last modified July 17 23:21 EDT 2019. Contains 325109 sequences. (Running on oeis4.)