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Beautiful proof

Posted: Sat Jan 01, 2005 5:25 am
by ranjit
Really nice proof. Thanks for it.

Posted: Sat Jan 01, 2005 6:52 am
by CodeMaker
Hi Cho, I am really interesed about your proof, but unfortunately I can't open the file format you have used. :cry: do you have any other file format like .pdf or plz mention what software will support the file, I will collect it then. :roll:

Posted: Sat Jan 01, 2005 8:04 am
by ..

Posted: Sat Jan 01, 2005 8:47 am
by Cho
CodeMaker wrote:do you have any other file format like .pdf
here is the pdf format: 10743.pdf

Re: 10743 - Blocks on Blocks

Posted: Sat Aug 14, 2010 2:11 am
by Angeh
hi alll ....
can somebody help
it doesnt work for n==999 ... returns negative number .....

Code: Select all

using namespace std;
const long long Mode=10000;
#define FOR(i,n) for(int i=0;i<n;++i)
long long matrix[3][3]={0,0,4,1,0,-7,0,1,5},result[3][3],temp[3][3];
void power(int n ){
	if(n==1) FOR(r,3)FOR(c,3)result[r][c]=matrix[r][c];
	else if(n%2==1){
		FOR(r,3)FOR(c,3)FOR(i,3)temp[r][c] = (temp[r][c]+result[r][i]*result[i][c])%Mode ;
		FOR(r,3)FOR(c,3)FOR(i,3)result[r][c] = (result[r][c] + temp[r][i]*matrix[i][c])%Mode;
	else {
		FOR(r,3)FOR(c,3)FOR(i,3)temp[r][c] = (temp[r][c] + result[r][i]*result[i][c] )%Mode;
	return ;
int main(){
	int cas,n,res;
	for(int ca=0;ca<cas;++ca){
		else if(n==2)res=2;
		else if(n==3)res=6;
		else if(n==4)res=19;
		else {
			res= ( result[0][2]*2 + result[1][2]*6 + result[2][2]*19 )%Mode;
		if(n<9)printf("Case %d: %d\n",ca+1,res);
		else printf("Case %d: %04d\n",ca+1,res);
	return 0;

Re: 10743 - Blocks on Blocks

Posted: Wed Nov 16, 2016 2:56 am
by dull_jester
Ok, from Cho's hints I've been able to go as far as this:

a_n = \sum_{k=1}^{n}b_{n,k},
b_{n,k} = \sum_{t=1}^{n-k}(t+k-1)b_{n-k,t}

I can take this one step further, but how to get to the formula a_n = ?a_{n-1} + ?a_{n-2} + ?a_{n-3}?
Cho's derivation is no longer accessible.