

A233773


Triangle read by rows in which row n lists the proper divisors of n together with n.


2



1, 1, 2, 1, 3, 1, 2, 4, 1, 5, 1, 2, 3, 6, 1, 7, 1, 2, 4, 8, 1, 3, 9, 1, 2, 5, 10, 1, 11, 1, 2, 3, 4, 6, 12, 1, 13, 1, 2, 7, 14, 1, 3, 5, 15, 1, 2, 4, 8, 16, 1, 17, 1, 2, 3, 6, 9, 18, 1, 19, 1, 2, 4, 5, 10, 20, 1, 3, 7, 21, 1, 2, 11, 22, 1, 23
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OFFSET

1,3


COMMENTS

The same as A027750 but with the last term of every row multiplied by 1.
The sum of row n gives the abundance of n.


LINKS

Table of n, a(n) for n=1..76.
Eric Weisstein's World of Mathematics, Abundance
Eric Weisstein's World of Mathematics, Quasiperfect Number


EXAMPLE

Written as an irregular triangle in which row n has length A000005(n) the sequence begins:
1;
1, 2;
1, 3;
1, 2, 4;
1, 5;
1, 2, 3, 6;
1, 7;
1, 2, 4, 8;
1, 3, 9;
1, 2, 5, 10;
1, 11;
1, 2, 3, 4, 6, 12;
...


MATHEMATICA

Flatten[Table[Join[{Most[Divisors[n]]}, {n}], {n, 30}]] (* Harvey P. Dale, Feb 20 2016 *)


CROSSREFS

Row sums give A033880.
Cf. A000005, A000203, A000396, A001065, A005100, A005101, A027750, A027751, A033879.
Cf. A137510, A163870.
Sequence in context: A169896 A210208 A162306 * A027750 A275055 A254679
Adjacent sequences: A233770 A233771 A233772 * A233774 A233775 A233776


KEYWORD

sign,tabf


AUTHOR

Omar E. Pol, Dec 31 2013


STATUS

approved



