A269065 Irregular triangle read by rows: row n lists divisors of n-th composite number.

1, 2, 4, 1, 2, 3, 6, 1, 2, 4, 8, 1, 3, 9, 1, 2, 5, 10, 1, 2, 3, 4, 6, 12, 1, 2, 7, 14, 1, 3, 5, 15, 1, 2, 4, 8, 16, 1, 2, 3, 6, 9, 18, 1, 2, 4, 5, 10, 20, 1, 3, 7, 21, 1, 2, 11, 22, 1, 2, 3, 4, 6, 8, 12, 24, 1, 5, 25, 1, 2, 13, 26, 1, 3, 9, 27, 1, 2, 4, 7, 14, 28, 1, 2, 3, 5, 6, 10, 15, 30, 1, 2, 4, 8, 16, 32, 1, 3, 11, 33, 1, 2, 17, 34

Offset

1,2

Comments

Subsequence of A027750.

Row sums give A073255.

Right border gives A002808.

Links

Table of n, a(n) for n=1..104.

Ilya Gutkovskiy, Extended example

Ilya Gutkovskiy, Graphic additions

Eric Weisstein's World of Mathematics, Composite Number

Eric Weisstein's World of Mathematics, Divisor

Index entries for sequences related to divisors of numbers

Example

Triangle begins:
1,  2,  4;
1,  2,  3,  6;
1,  2,  4,  8;
1,  3,  9;
1,  2,  5,  10;
1,  2,  3,  4,  6,  12;
1,  2,  7,  14;
1,  3,  5,  15
1,  2,  4,  8,  16;
1,  2,  3,  6,  9,  18;
1,  2,  4,  5,  10, 20;
1,  3,  7,  21;
1,  2,  11, 22;
1,  2,  3,  4,  6,  8,  12, 24;
1,  5,  25;
1,  2,  13, 26;
1,  3,  9,  27;
1,  2,  4,  7,  14, 28;
1,  2,  3,  5,  6,  10, 15, 30;
1,  2,  4,  8,  16, 32;
1,  3,  11, 33;
1,  2,  17, 34;
...

Mathematica

Flatten[Table[Divisors[Composite[n]], {n, 22}]]

Prog

(PARI) tabf(nn) =  forcomposite(c=1, nn, print(divisors(c), ", ")); \\ Michel Marcus, Feb 21 2016

Crossrefs

Cf. A002808, A027750, A035004 (row length), A133021, A133031, A138881.

Sequence in context: A053450 A352533 A215905 * A206475 A227184 A124911

Adjacent sequences: A269062 A269063 A269064 * A269066 A269067 A269068

Keyword

nonn,tabf

Author

Ilya Gutkovskiy, Feb 21 2016

Status

approved