

A272025


Irregular triangle read by rows, n>=1, 1<=k<=A038548(n), in which T(n,k) is the sum of the kth pair of conjugate divisors of n, or T(n,k) is the central divisor of n if such pair does not exist.


0



1, 3, 4, 5, 2, 6, 7, 5, 8, 9, 6, 10, 3, 11, 7, 12, 13, 8, 7, 14, 15, 9, 16, 8, 17, 10, 4, 18, 19, 11, 9, 20, 21, 12, 9, 22, 10, 23, 13, 24, 25, 14, 11, 10, 26, 5, 27, 15, 28, 12, 29, 16, 11, 30, 31, 17, 13, 11, 32, 33, 18, 12, 34, 14, 35, 19, 36, 12, 37, 20, 15, 13, 6, 38, 39, 21, 40, 16, 41, 22, 14, 13, 42, 43, 23, 17, 13
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OFFSET

1,2


LINKS

Table of n, a(n) for n=1..87.
Omar E. Pol, Illustration of the divisors of the first 12 positive integers
Index entries for sequences related to sigma(n)


EXAMPLE

Triangle begins:
1;
3;
4;
5, 2;
6;
7, 5;
8;
9, 6;
10, 3;
11, 7;
12;
13, 8, 7;
...
For n = 9 the divisors of 9 are [1, 3, 9]. There is only one pair of conjugate divisors: [1, 9], and the central divisor is 3, so the 9th row of triangle is [10, 3].
For n = 12 the divisors of 12 are [1, 2, 3, 4, 6, 12]. There are three pairs of conjugate divisors, they are [1, 12], [2, 6], [3, 4], so the 12th row of triangle is [13, 8, 7].


CROSSREFS

Row sums give A000203.
Row lengths give A038548.
Right border gives A207376.
Column 1 is A065475.
Cf. A027750, A210959, A228814.
Sequence in context: A239639 A099816 A237273 * A262411 A280488 A250072
Adjacent sequences: A272022 A272023 A272024 * A272026 A272027 A272028


KEYWORD

nonn,tabf


AUTHOR

Omar E. Pol, Apr 21 2016


STATUS

approved



