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A210208 Triangle read by rows in which row n lists the divisors of n that are prime powers, A000961. 8
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 (list; graph; refs; listen; history; text; internal format)
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: A222818 A057059 A169896 * A162306 A233773 A027750

Adjacent sequences:  A210205 A210206 A210207 * A210209 A210210 A210211

KEYWORD

nonn,tabf

AUTHOR

Reinhard Zumkeller, Mar 18 2012

STATUS

approved

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Last modified October 23 19:26 EDT 2018. Contains 316530 sequences. (Running on oeis4.)