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A299766 Greatest odd noncomposite divisor of n. 2
1, 1, 3, 1, 5, 3, 7, 1, 3, 5, 11, 3, 13, 7, 5, 1, 17, 3, 19, 5, 7, 11, 23, 3, 5, 13, 3, 7, 29, 5, 31, 1, 11, 17, 7, 3, 37, 19, 13, 5, 41, 7, 43, 11, 5, 23, 47, 3, 7, 5, 17, 13, 53, 3, 11, 7, 19, 29, 59, 5, 61, 31, 7, 1, 13, 11, 67, 17, 23, 7, 71, 3, 73, 37, 5, 19, 11, 13, 79, 5, 3, 41, 83, 7, 17, 43 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

The sequence can be constructed replacing the 2's with 1's in A006530.

LINKS

Table of n, a(n) for n=1..86.

FORMULA

a(n) = A006530(A000265(n)). - Michel Marcus, Mar 15 2018

a(n) = 1 for n in A000079 (powers of 2). - Michel Marcus, Apr 14 2018

MAPLE

A299766 := proc(n)

    local dvs ;

    dvs := sort(convert(numtheory[factorset](n) minus {2}, list)) ;

    if nops(dvs) >= 1 then

        op(-1, dvs) ;

    else

        1;

    end if;

end proc: # R. J. Mathar, May 05 2018

MATHEMATICA

Array[FactorInteger[#][[-1, 1]] /. 2 -> 1 &, 86] (* Michael De Vlieger, Mar 16 2018 *)

PROG

(PARI) a(n) = my(m = n >> valuation(n, 2)); if (m==1, 1, vecmax(factor(m)[, 1])); \\ Michel Marcus, Mar 15 2018

(MAGMA) [#f eq 1 select 1 else f[#f][1] where f is Factorization(2*n): n in [1..90]]; // Vincenzo Librandi, Mar 20 2018

CROSSREFS

Cf. A000265 (odd part), A008578 (noncomposite numbers), A006005 (odd noncomposite numbers), A006530 (greatest noncomposite divisor).

Sequence in context: A308655 A217663 A078701 * A161398 A204455 A318653

Adjacent sequences:  A299763 A299764 A299765 * A299767 A299768 A299769

KEYWORD

nonn,easy

AUTHOR

Omar E. Pol, Mar 12 2018

STATUS

approved

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Last modified July 31 22:39 EDT 2021. Contains 346377 sequences. (Running on oeis4.)