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A133829 a(n) = the largest "non-isolated divisor" of 2n. A positive divisor k of n is non-isolated if k-1 or k+1 also divides n. 2
2, 2, 3, 2, 2, 4, 2, 2, 3, 5, 2, 4, 2, 2, 6, 2, 2, 4, 2, 5, 7, 2, 2, 4, 2, 2, 3, 8, 2, 6, 2, 2, 3, 2, 2, 9, 2, 2, 3, 5, 2, 7, 2, 2, 10, 2, 2, 4, 2, 5, 3, 2, 2, 4, 11, 8, 3, 2, 2, 6, 2, 2, 7, 2, 2, 12, 2, 2, 3, 5, 2, 9, 2, 2, 6, 2, 2, 13, 2, 5, 3, 2, 2, 8, 2, 2, 3, 2, 2, 10, 14, 2, 3, 2, 2, 4, 2, 2, 3 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

No odd integer has any non-isolated divisors.

LINKS

Table of n, a(n) for n=1..99.

MAPLE

A133829 := proc(n) local divs, k, i ; divs := sort(convert(numtheory[divisors](2*n), list)) ; for i from 1 to nops(divs) do k := op(-i, divs) ; if k-1 in divs or k+1 in divs then RETURN(k) ; fi ; od: RETURN(0) ; end: seq(A133829(n), n=1..100) ; # R. J. Mathar, Oct 19 2007

CROSSREFS

Cf. A133780, A133828.

Sequence in context: A281908 A106441 A131836 * A160651 A230296 A278317

Adjacent sequences:  A133826 A133827 A133828 * A133830 A133831 A133832

KEYWORD

nonn

AUTHOR

Leroy Quet, Sep 25 2007

EXTENSIONS

More terms from R. J. Mathar, Oct 19 2007

STATUS

approved

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Last modified July 4 15:25 EDT 2020. Contains 335448 sequences. (Running on oeis4.)