A210208 Triangle read by rows in which row n lists the divisors of n that are prime powers, A000961.

1, 1, 2, 1, 3, 1, 2, 4, 1, 5, 1, 2, 3, 1, 7, 1, 2, 4, 8, 1, 3, 9, 1, 2, 5, 1, 11, 1, 2, 3, 4, 1, 13, 1, 2, 7, 1, 3, 5, 1, 2, 4, 8, 16, 1, 17, 1, 2, 3, 9, 1, 19, 1, 2, 4, 5, 1, 3, 7, 1, 2, 11, 1, 23, 1, 2, 3, 4, 8, 1, 5, 25, 1, 2, 13, 1, 3, 9, 27, 1, 2, 4, 7

Offset

1,3

Comments

A073093(n) = length of n-th row;

A023888(n) = sum of n-th row;

A183091(n) = product of n-th row;

A034699(n) = T(n,A073093(n)) = maximum of n-th row;

{T(n,k):k=1..A073093(n)} subset of {A027750(n,k):k=1..A000005(n)} for all n.

Links

Reinhard Zumkeller, Rows n=1..5000 of triangle, flattened

Eric Weisstein's World of Mathematics, Divisor

Example

 1;
 1, 2;
 1, 3;
 1, 2, 4;
 1, 5;
 1, 2, 3;
 1, 7;
 1, 2, 4, 8;
 1, 3, 9;
 1, 2, 5;
 1, 11;
 1, 2, 3, 4; - Geoffrey Critzer, Feb 08 2015

Mathematica

Table[Prepend[Select[Divisors[n], PrimeNu[#] == 1 &], 1], {n, 1, 10}]//Grid (* Geoffrey Critzer, Feb 08 2015 *)

Prog

(Haskell)
a210208 n k = a210208_tabf !! (n-1) !! (n-1)
a210208_row n = a210208_tabf !! (n-1)
a210208_tabf = map (filter ((== 1) . a010055)) a027750_tabf

Crossrefs

Cf. A010055, A141809.

Sequence in context: A346795 A361172 A169896 * A162306 A376248 A348135

Adjacent sequences: A210205 A210206 A210207 * A210209 A210210 A210211

Keyword

nonn,tabf

Author

Reinhard Zumkeller, Mar 18 2012

Status

approved