A278235 Filter-sequence for factorial base (digit levels): Least number with the same prime signature as A275735(n).

1, 2, 2, 4, 2, 6, 2, 4, 4, 8, 6, 12, 2, 6, 6, 12, 4, 12, 2, 6, 6, 12, 6, 30, 2, 4, 4, 8, 6, 12, 4, 8, 8, 16, 12, 24, 6, 12, 12, 24, 12, 36, 6, 12, 12, 24, 30, 60, 2, 6, 6, 12, 4, 12, 6, 12, 12, 24, 12, 36, 4, 12, 12, 36, 8, 24, 6, 30, 30, 60, 12, 60, 2, 6, 6, 12, 6, 30, 6, 12, 12, 24, 30, 60, 6, 30, 30, 60, 12, 60, 4, 12, 12, 36, 12, 60, 2, 6, 6, 12, 6, 30, 6

Offset: 0

Author

Antti Karttunen, Nov 16 2016

Keywords

• nonn

Comments

This sequence can be used for filtering certain factorial base (A007623) related sequences, because it matches only with any such sequence b that can be computed as b(n) = f(A275735(n)), where f(n) is any function that depends only on the prime signature of n (some of these are listed under the index entry for "sequences computed from exponents in ...").

Matching in this context means that the sequence a matches with the sequence b iff for all i, j: a(i) = a(j) => b(i) = b(j). In other words, iff the sequence b partitions the natural numbers to the same or coarser equivalence classes (as/than the sequence a) by the distinct values it obtains.

Links

• Antti Karttunen, Table of n, a(n) for n = 0..40320
• Indranil Ghosh, Python program for computing this sequence
• Index entries for sequences computed from exponents in factorization of n
• Index entries for sequences related to factorial base representation

Crossrefs

Cf. A046523, A225901, A275735.

Other factorial base related filter-sequences: A278225, A278234, A278236.

Sequences that partition N into same or coarser equivalence classes: A060130, A257696 (?), A264990, A275806, A275948, A275964 (this is a proper a subset of the sequences that match with A278236).

Programs

Scheme

(define (A278235 n) (A046523 (A275735 n)))

Formula

a(n) = A046523(A275735(n)).

a(n) = A278234(A225901(n)).