A028308 Form a triangle with n numbers in top row; all other numbers are the product of their parents. The numbers must be positive and distinct and the final number is to be minimized.

1, 6, 48, 4320, 46448640, 10835538739200000, 2672817951712314077919313920000000

Offset

1,2

Comments

The next term has 69 digits. - Charlie Neder, Mar 09 2019

Links

Table of n, a(n) for n=1..7.

Problem 401 here suggested this sequence

Example

Solutions for n=1,2,... are 1; 2 3; 3 2 4; 4 2 3 5; 5 3 2 4 7
Example triangle for a(4):
   4    2    3    5
     8    6    15
       48    90
         4320
Some solutions for a(6) and a(7) are (7,4,3,2,5,8) and (9,7,4,2,3,5,10), and others can be created by interchanging opposite numbers (e.g., swapping 5 and 7 in the second set). - Charlie Neder, Mar 09 2019

Crossrefs

A less interesting cousin of A028307.

Sequence in context: A324461 A084259 A372454 * A173011 A061429 A048357

Adjacent sequences: A028305 A028306 A028307 * A028309 A028310 A028311

Keyword

nonn

Author

N. J. A. Sloane

Extensions

a(7) and example removed from title by Charlie Neder, Mar 09 2019

Status

approved