increasing or decreasing subsequence
bouyao
bouyao at wanadoo.fr
Sat Mar 13 02:06:06 CET 2004
Dear seqfan,
if we denote S(n) concatenation of numbers
How many increasing subsequence we can extract of S(n) ?
Examples S(n) = successive numbers
S(6) = 123456
increasing subsequence are :
1,2,3,4,5,6
1,2,3,4,56
1,2,3,456
1,2,34,56
1,2,3456
1,23,456
1,23456
12,34,56
12,3456
123,456
123456
for n=6 whe have 11 increasing subsequences (a(6)=11)
and our sequence is 1,2,3,5,7,11,15,22,51,...
if S(n) is concatenation of prime numbers
our sequence is 1,2,3,5,8,14,25
this sequence are not in OEIS
How many decreasing or increasing subsequence we can extract of S(n)
If S(n) is succesive numbers
If S(n) is prime numbers
If S(n) is odd or even numbers ?
we can apply several sequence
Thanks
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