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A027749 Take the list 1,2,3,4,... and replace each n with all d > 1 that divide n. 4
1, 2, 3, 2, 4, 5, 2, 3, 6, 7, 2, 4, 8, 3, 9, 2, 5, 10, 11, 2, 3, 4, 6, 12, 13, 2, 7, 14, 3, 5, 15, 2, 4, 8, 16, 17, 2, 3, 6, 9, 18, 19, 2, 4, 5, 10, 20, 3, 7, 21, 2, 11, 22, 23, 2, 3, 4, 6, 8, 12, 24, 5, 25, 2, 13, 26, 3, 9, 27, 2, 4, 7, 14, 28, 29, 2, 3, 5, 6, 10, 15, 30, 31, 2, 4, 8, 16, 32, 3, 11, 33, 2, 17, 34, 5, 7, 35 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(A002541(n)+1)=n; a(A002541(n)+2)=A020639(n+1). - Reinhard Zumkeller, Nov 22 2003

Seen as a triangle read by rows: T(1,1)=1 and T(n,k)=A027750(n,k+1) for n>1, 1<=k<A000005(n). - Reinhard Zumkeller, Oct 01 2012

LINKS

Reinhard Zumkeller, Rows n = 1..250 of triangle, flattened

MATHEMATICA

Join[{1}, Flatten[Rest[Divisors[#]]&/@Range[40]]] (* Harvey P. Dale, Jun 28 2011 *)

PROG

(Haskell)

a027749 n k = a027749_tabf !! (n-1) !! (k-1)

a027749_row n = a027749_tabf !! n

a027749_tabf = [1] : map tail (tail a027750_tabf)

-- Reinhard Zumkeller, Oct 01 2012, Oct 19 2011, Jul 11 2011

CROSSREFS

Cf. A032741, A027750.

Sequence in context: A071515 A121998 A120499 * A226208 A214540 A214595

Adjacent sequences:  A027746 A027747 A027748 * A027750 A027751 A027752

KEYWORD

nonn,easy,nice,tabf

AUTHOR

N. J. A. Sloane

EXTENSIONS

More terms from Scott Lindhurst (ScottL(AT)alumni.princeton.edu)

Keyword tabf added by Reinhard Zumkeller, Oct 01 2012

STATUS

approved

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Last modified February 19 16:56 EST 2018. Contains 299356 sequences. (Running on oeis4.)