A374250 Greatest sum of run-compression of a permutation of the prime factors of n.

0, 2, 3, 2, 5, 5, 7, 2, 3, 7, 11, 7, 13, 9, 8, 2, 17, 8, 19, 9, 10, 13, 23, 7, 5, 15, 3, 11, 29, 10, 31, 2, 14, 19, 12, 10, 37, 21, 16, 9, 41, 12, 43, 15, 11, 25, 47, 7, 7, 12, 20, 17, 53, 8, 16, 11, 22, 31, 59, 12, 61, 33, 13, 2, 18, 16, 67, 21, 26, 14, 71

Offset

1,2

Comments

We define the run-compression of a sequence to be the anti-run obtained by reducing each run of repeated parts to a single part. Alternatively, run-compression removes all parts equal to the part immediately to their left. For example, (1,1,2,2,1) has run-compression (1,2,1).

Links

Table of n, a(n) for n=1..71.

Formula

a(n) = A001414(n) iff n belongs to A335433 (the separable case, complement A335448), row-sums of A027746.

Example

The prime factors of 24 are {2,2,2,3}, with permutations such as (2,2,3,2) whose run-compression sums to 7, so a(24) = 7.
The prime factors of 216 are {2,2,2,3,3,3}, with permutations such as (2,3,2,3,2,3) whose run-compression sums to 15, so a(216) = 15.

Mathematica

prifacs[n_]:=If[n==1, {}, Flatten[ConstantArray@@@FactorInteger[n]]];
Table[Max@@(Total[First/@Split[#]]& /@ Permutations[prifacs[n]]), {n, 100}]

Crossrefs

Positions of 2 are A000079 (powers of two) except 1.

Positions of 3 are A000244 (powers of three) except 1.

For least instead of greatest sum of run-compression we have A008472.

For prime indices instead of factors we have A373956.

For number of runs instead of sum of run-compression we have A373957.

A001221 counts distinct prime factors, A001222 with multiplicity.

A003242 counts run-compressed compositions, i.e., anti-runs.

A007947 (squarefree kernel) represents run-compression of multisets.

A008480 counts permutations of prime factors (or prime indices).

A056239 adds up prime indices, row sums of A112798.

A116861 counts partitions by sum of run-compression.

A304038 lists run-compression of prime indices, sum A066328.

A335433 lists numbers whose prime indices are separable, complement A335448.

A373949 counts compositions by sum of run-compression, opposite A373951.

A374251 run-compresses standard compositions, sum A373953, rank A373948.

Cf. A000040, A001223, A001414, A037201, A116608, A124767, A333755, A373954, A374246, A374247, A374252.

Sequence in context: A008472 A318675 A123528 * A074036 A074251 A074196

Adjacent sequences: A374247 A374248 A374249 * A374251 A374252 A374253

Keyword

nonn

Author

Gus Wiseman, Jul 09 2024

Status

approved