A232743 - OEIS

A232743

Numbers n for which the largest m such that (m-1)! divides n is a composite number > 5.

120, 240, 360, 480, 600, 840, 960, 1080, 1200, 1320, 1560, 1680, 1800, 1920, 2040, 2280, 2400, 2520, 2640, 2760, 3000, 3120, 3240, 3360, 3480, 3720, 3840, 3960, 4080, 4200, 4440, 4560, 4680, 4800, 4920, 5040, 5160, 5280, 5400, 5520, 5640, 5880, 6000, 6120, 6240

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OFFSET

1,1

COMMENTS

Numbers n for which A055881(n)>4 and is one of the terms of A072668.

Numbers n for which two plus the number of the trailing zeros in their factorial base representation A007623(n) is a composite number larger than 5.

All terms are multiples of 120. Specifically, these are all those terms of A232742 which are divisible by 120 (or equally: 24).

Please see also the comments in A055926, whose subset this sequence is.

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..25920

EXAMPLE

120 is included because A055881(120)=5 and 5+1 is a composite number larger than 5. Note that A007623(120) = '10000', with four trailing zeros.

720 is the first missing multiple of 120, as A055881(720)=6 and 7 is a prime, not composite, so 720 is not included in this sequence. Note that A007623(720) = '100000', with five trailing zeros, and 5+2 is not a composite.

120960 (= 3*8!) is included because A055881(120960)=8 and 9 is a composite number larger than 5. Note that A007623(120960) = '30000000', with seven trailing zeros.

PROG

(Scheme, with Antti Karttunen's IntSeq-library)

(define A232743 (MATCHING-POS 1 1 (lambda (n) (cond ((A055881 n) => (lambda (k) (and (> k 4) (not (prime? (+ k 1))))))))))

CROSSREFS

Subset of both A232742 and A055926.

Cf. also A007623, A055881, A230403, A232744-A232745.

Sequence in context: A084142 A349745 A256814 * A146950 A028976 A158130

Adjacent sequences: A232740 A232741 A232742 * A232744 A232745 A232746

KEYWORD

nonn

AUTHOR

Antti Karttunen, Dec 01 2013

STATUS

approved