A218707 First number beginning the smallest chain of n consecutive even divisors distanced no more than 2 one from each other, with no odd divisors between, of some factorial s!.

2, 4, 4, 6, 304, 680, 1054, 1558, 15904, 41638, 82800, 241898, 241898, 241898, 241898

Offset

1,1

Comments

Minimal s are respectively : 2, 4, 4, 5, 31, 43, 59, 157, 379, 631, 2179, 2479, 2479, 2479, 2479.

Maximal s are : 2, 4, 4, 5, 61 - 1, 53 - 1, 71 - 1, 223 - 1 , 1061 - 1, 661 - 1, 2671 - 1, 4937 - 1, 4937 - 1, 4937 - 1, 4937 - 1.

Links

Table of n, a(n) for n=1..15.

Example

6, 8, 10, 12 is the smallest chain of length 4 of even divisors of factorials s! with no odd divisor between, for only s = 5.

Crossrefs

Cf. A218493.

Sequence in context: A179112 A359119 A096612 * A177153 A164719 A104510

Adjacent sequences: A218704 A218705 A218706 * A218708 A218709 A218710

Keyword

nonn

Author

Robin Garcia, Nov 04 2012

Status

approved