|
Search: id:A035470
|
|
|
| A035470 |
|
Number of ways to break {1,2,3,...n} into sets with equal sums. |
|
+0
5
|
|
| 1, 1, 2, 2, 2, 2, 6, 12, 11, 2, 80, 166, 2, 665, 2918, 3309, 9296, 23730, 31875, 301030, 422897, 2, 13716867, 71504980, 100664385, 54148591, 880696662, 498017759, 27450476787, 111911522819, 179459955554, 2144502175214, 59115423983
(list; graph; listen)
|
|
|
OFFSET
|
1,3
|
|
|
COMMENT
|
a(n) = 2 <=> |{d|n*(n+1)/2 : d>=n}| = 2. [From Alois P. Heinz (heinz(AT)hs-heilbronn.de), Sep 03 2009]
|
|
EXAMPLE
|
a(7)=6 since we have 1234567, 16/25/34/7, 167/2345, 257/1346, 347/1256, 356/1247
|
|
MAPLE
|
with (numtheory): b:= proc() option remember; local i, j, t; `if` (args[1]=0, `if` (nargs=2, 1, b(args[t] $t=2..nargs)), add (`if` (args[j] -args[nargs] <0, 0, b(sort ([seq (args[i] -`if` (i=j, args[nargs], 0), i=1..nargs-1)])[], args[nargs]-1)), j=1..nargs-1)) end: a:= proc(n) local i, m, x; m:= n*(n+1)/2; 1+ add (b(i$(m/i), n)/(m/i)!, i=[select (x-> x>=n, divisors(m) minus {m})[]]) end: seq (a(n), n=1..25); [From Alois P. Heinz (heinz(AT)hs-heilbronn.de), Sep 03 2009]
|
|
CROSSREFS
|
Cf. A164977, A164978. [From Alois P. Heinz (heinz(AT)hs-heilbronn.de), Sep 03 2009]
Sequence in context: A078014 A063867 A024723 this_sequence A061292 A138068 A054083
Adjacent sequences: A035467 A035468 A035469 this_sequence A035471 A035472 A035473
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Erich Friedman (erich.friedman(AT)stetson.edu)
|
|
EXTENSIONS
|
More terms from John W. Layman (layman(AT)math.vt.edu), Mar 18 2002
a(19) - a(33) from Alois P. Heinz (heinz(AT)hs-heilbronn.de), Sep 03 2009
|
|
|
Search completed in 0.002 seconds
|
