|
|
A133927
|
|
Numbers k such that the sum of the first k Catalan numbers, C_1 + C_2 + ... + C_k, is divisible by k.
|
|
0
|
|
|
|
OFFSET
|
1,2
|
|
COMMENTS
|
The sum of the first 30 Catalan numbers, 1 + 2 + 5 + ... + 3814986502092304 = 5175497420902740, is divisible by 30, so 30 is a term.
|
|
LINKS
|
|
|
MATHEMATICA
|
Module[{nn=40000, lst}, lst=Thread[{Range[nn], Accumulate[CatalanNumber[Range[nn]]]}]; Position[ lst, _?(Mod[#[[2]], #[[1]]]==0&), 1, Heads->False]]//Flatten (* The program generates the first 5 terms of the sequence. *) (* Harvey P. Dale, Jun 18 2024 *)
|
|
CROSSREFS
|
|
|
KEYWORD
|
hard,more,nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|