A027749 Take the list 1,2,3,4,... and replace each n with all d > 1 that divide n.

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

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: A121998 A120499 A377485 * A226208 A304743 A214540

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