cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A343662 Irregular triangle read by rows where T(n,k) is the number of strict length k chains of divisors of n, 0 <= k <= Omega(n) + 1.

This page as a plain text file.
%I A343662 #7 May 01 2021 21:55:36
%S A343662 1,1,1,2,1,1,2,1,1,3,3,1,1,2,1,1,4,5,2,1,2,1,1,4,6,4,1,1,3,3,1,1,4,5,
%T A343662 2,1,2,1,1,6,12,10,3,1,2,1,1,4,5,2,1,4,5,2,1,5,10,10,5,1,1,2,1,1,6,12,
%U A343662 10,3,1,2,1,1,6,12,10,3,1,4,5,2,1,4,5,2
%N A343662 Irregular triangle read by rows where T(n,k) is the number of strict length k chains of divisors of n, 0 <= k <= Omega(n) + 1.
%e A343662 Triangle begins:
%e A343662    1:  1  1
%e A343662    2:  1  2  1
%e A343662    3:  1  2  1
%e A343662    4:  1  3  3  1
%e A343662    5:  1  2  1
%e A343662    6:  1  4  5  2
%e A343662    7:  1  2  1
%e A343662    8:  1  4  6  4  1
%e A343662    9:  1  3  3  1
%e A343662   10:  1  4  5  2
%e A343662   11:  1  2  1
%e A343662   12:  1  6 12 10  3
%e A343662   13:  1  2  1
%e A343662   14:  1  4  5  2
%e A343662   15:  1  4  5  2
%e A343662   16:  1  5 10 10  5  1
%e A343662 For example, row n = 12 counts the following chains:
%e A343662   ()  (1)   (2/1)   (4/2/1)   (12/4/2/1)
%e A343662       (2)   (3/1)   (6/2/1)   (12/6/2/1)
%e A343662       (3)   (4/1)   (6/3/1)   (12/6/3/1)
%e A343662       (4)   (4/2)   (12/2/1)
%e A343662       (6)   (6/1)   (12/3/1)
%e A343662       (12)  (6/2)   (12/4/1)
%e A343662             (6/3)   (12/4/2)
%e A343662             (12/1)  (12/6/1)
%e A343662             (12/2)  (12/6/2)
%e A343662             (12/3)  (12/6/3)
%e A343662             (12/4)
%e A343662             (12/6)
%t A343662 Table[Length[Select[Reverse/@Subsets[Divisors[n],{k}],And@@Divisible@@@Partition[#,2,1]&]],{n,15},{k,0,PrimeOmega[n]+1}]
%Y A343662 Column k = 1 is A000005.
%Y A343662 Row ends are A008480.
%Y A343662 Row lengths are A073093.
%Y A343662 Column k = 2 is A238952.
%Y A343662 The case from n to 1 is A334996 or A251683 (row sums: A074206).
%Y A343662 A non-strict version is A334997 (transpose: A077592).
%Y A343662 The case starting with n is A337255 (row sums: A067824).
%Y A343662 Row sums are A337256 (nonempty: A253249).
%Y A343662 A001055 counts factorizations.
%Y A343662 A001221 counts distinct prime factors.
%Y A343662 A001222 counts prime factors with multiplicity.
%Y A343662 A097805 counts compositions by sum and length.
%Y A343662 A122651 counts strict chains of divisors summing to n.
%Y A343662 A146291 counts divisors of n with k prime factors (with multiplicity).
%Y A343662 A163767 counts length n - 1 chains of divisors of n.
%Y A343662 A167865 counts strict chains of divisors > 1 summing to n.
%Y A343662 A337070 counts strict chains of divisors starting with superprimorials.
%Y A343662 Cf. A002033, A007425, A007426, A051026, A062319, A143773, A186972, A327527, A337074, A337105, A337107, A343658.
%K A343662 nonn,tabf
%O A343662 1,4
%A A343662 _Gus Wiseman_, May 01 2021