OFFSET
2,4
COMMENTS
Each row has d(n)-1 terms, where d(n) is the number of positive divisors of n. The first row listed is row 2.
LINKS
Michael De Vlieger, Table of n, a(n) for n = 2..15955 (rows 2 <= n <= 2310)
EXAMPLE
The positive divisors of 20 are 1,2,4,5,10,20. GCD(1,2)=1. GCD(2,4)=2. GCD(4,5)=1. GCD(5,10)=5. And GCD(10,20)=10. So row 20 is (1,2,1,5,10).
From R. J. Mathar, Jul 20 2009: (Start)
The table starts
1
1
1,2
1
1,1,3
1
1,2,4
1,3
1,1,5
1
1,1,1,2,6
(End)
MAPLE
A136178row := proc(n) local dvs; dvs := sort(convert(numtheory[divisors](n), list)) ; seq(gcd(op(d-1, dvs), op(d, dvs)), d=2..nops(dvs)) ; end: seq(A136178row (n), n=1..70) ; # R. J. Mathar, Jul 20 2009
MATHEMATICA
Table[Map[GCD @@ # &, Partition[Divisors@ n, 2, 1]], {n, 2, 36}] // Flatten (* Michael De Vlieger, Sep 21 2017 *)
PROG
(PARI) row(n) = my(d=divisors(n)); vector(#d-1, k, gcd(d[k], d[k+1]));
tabf(nn) = for(n=2, nn, print(row(n))); \\ Michel Marcus, Sep 22 2017
CROSSREFS
KEYWORD
nonn,tabf
AUTHOR
Leroy Quet, Dec 19 2007
EXTENSIONS
Keyword:tabl replaced with keyword:tabf by R. J. Mathar, Jul 22 2009
Extended beyond row 10 by R. J. Mathar, Jul 20 2009
STATUS
approved