login
A153787
Largest proper divisor of Motzkin number A001006(n).
1
1, 2, 3, 7, 17, 1, 19, 167, 1094, 2899, 1, 13945, 56817, 155286, 284489, 785593, 3268191, 9099642, 16950673, 47515853, 133587741, 376586805, 1064242599, 1291914643, 12834909238, 36503886401, 1944142787, 19152993059, 1144562017
OFFSET
2,2
LINKS
MAPLE
with(numtheory): M := proc (n) options operator, arrow: (sum((-1)^j*binomial(n+1, j)*binomial(2*n-3*j, n), j = 0 .. floor((1/3)*n)))/(n+1) end proc: seq(divisors(M(i))[tau(M(i))-1], i = 2 .. 32); # Emeric Deutsch, Jan 18 2009
MATHEMATICA
mot[0] = 1; mot[n_] := mot[n] = mot[n - 1] + Sum[mot[k] * mot[n - 2 - k], {k, 0, n - 2}]; lpd[n_] := n / FactorInteger[n][[1, 1]]; Table[lpd[mot[n]], {n, 2, 30}] (* Amiram Eldar, Nov 26 2019 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Omar E. Pol, Jan 16 2009
EXTENSIONS
Extended by Emeric Deutsch, Jan 18 2009
a(23)-a(27) and a(29)-a(30) corrected by Amiram Eldar, Nov 26 2019
STATUS
approved