A175340 -id:A175340 - cp's OEIS frontend

A190892 Numbers that can be written as ab = cd*e, where a, b, c, d, and e are distinct composite numbers.

192, 216, 240, 288, 320, 336, 360, 384, 432, 448, 480, 504, 528, 540, 560, 576, 600, 624, 640, 648, 672, 704, 720, 756, 768, 792, 800, 810, 816, 832, 840, 864, 880, 896, 900, 912, 936, 960, 972, 1000, 1008, 1024, 1040, 1056, 1080, 1088, 1104, 1120, 1134

Offset: 1

T. D. Noe, May 23 2011

nonn

Similar to A175340, but without the requirement that the composite numbers be consecutive. In this case, the k in A175340 can be taken to be 2.

Almost all numbers are in this sequence. Its complement has density O(n (log log n)^4/log n). - Charles R Greathouse IV, May 23 2011

			192 = 12*16 = 4*6*8.

T. D. Noe, Table of n, a(n) for n = 1..1000

Cf. A162247 (all factorizations of numbers), A175340.

A339245 is a subsequence.

A342876 Numbers that can be written as a product of k consecutive composite numbers and also of k+1 consecutive composite numbers, for some k>1.

Original entry on oeis.org

1680, 4320, 120960, 166320, 175560, 215760, 725760, 1814400, 1080647568000, 104613949440000, 115880067072000

Offset: 1

David A. Corneth, Mar 28 2021

Similar to but different from A175340 which has an additional condition that says that factors cannot be used twice. So 1814400 is here via 8*9*10*12*14*15 = 15*16*18*20*21 but not there as 15 is used twice.
This sequence is infinite. Proof:
Choose two consecutive composites c1 and c2 such that c1 < c2. Let S be the composites strictly between c2 and c1 * c2. Let product(S) be the product of terms in S. Then c1 * c2 * product(S) is a term.

Cf. A175340.

cp's OEIS Frontend

A190892 Numbers that can be written as ab = cd*e, where a, b, c, d, and e are distinct composite numbers.

Views

Author

Keywords

Comments

Examples

Links

Crossrefs

A342876 Numbers that can be written as a product of k consecutive composite numbers and also of k+1 consecutive composite numbers, for some k>1.

Views

Author

Keywords

Comments

Crossrefs

cp's OEIS Frontend

A190892 Numbers that can be written as a*b = c*d*e, where a, b, c, d, and e are distinct composite numbers.

Views

Author

Keywords

Comments

Examples

Links

Crossrefs

A342876 Numbers that can be written as a product of k consecutive composite numbers and also of k+1 consecutive composite numbers, for some k>1.

Views

Author

Keywords

Comments

Crossrefs

A190892 Numbers that can be written as ab = cd*e, where a, b, c, d, and e are distinct composite numbers.