#include #define be(v) (v).begin(),(v).end() #define pb(q) push_back(q) typedef long long ll; using namespace std; const ll mod=1000000007, INF=(1LL<<60); #define doublecout(a) cout< d; UnionFind(int n=0): d(n,-1) {} int find(int x) { if (d[x] < 0) return x; return d[x] = find(d[x]); } bool unite(int x, int y) { x = find(x); y = find(y); if (x == y) return false; if (d[x] > d[y]) swap(x,y); d[x] += d[y]; d[y] = x; return true; } bool same(int x, int y) { return find(x) == find(y);} int size(int x) { return -d[find(x)];} }; int count(vector v){ v.pb(0); int ret = 0; bool f = false; for(int i : v){ if(i) f = true; else if(f) ret++, f = false; } return ret; } vector paint(vector &a, vector &b){ int id = 0, n = a.size(); vector ret(n, 0); bool f = false; for(int i=0;i color(vector &a, vector &b){ int n = a.size(); vector ans(n,0); int ma = 0; rep(i,n) ma = max(ma,a[i]); vector> ar(ma,vector(0)); vector ok(ma, false); rep(i, n){ if (a[i] != 0){ if (b[i] == 1) ok[a[i] - 1] = true; ar[a[i] - 1].emplace_back(i); } } rep(i, ma) if (!ok[i]) return ans; UnionFind tree(n); repp(i, n, 1) if(b[i-1] == 1 && b[i] == 1) tree.unite(i - 1, i); rep(i,ma){ auto &r = ar[i]; repp(j, r.size(), 1) tree.unite(r[0], r[j]); } int ima = 1; map mp; rep(i, n){ if (b[i] == 0) ans[i] = 0; else { int ne = tree.find(i); if (mp.find(ne) == mp.end()){ mp[ne] = ima; ans[i] = ima; ima++; } else { ans[i] = mp[ne]; } } } return ans; } struct dat{ set s; stack st; vector an; set stin; int ima; }; vector> komo(int n){ vector> ret; queue que; dat a; a.ima = 2; a.s.insert(1); que.push(a); while (!que.empty()){ dat q = que.front(); que.pop(); if (q.an.size() == n){ ret.emplace_back(q.an); continue; } for (auto itr = q.s.begin(); itr != q.s.end(); itr++){ dat p = q; int m = *itr; if (p.stin.find(m) == p.stin.end()){ p.an.emplace_back(m); p.stin.insert(m); p.st.push(m); if (m == p.ima -1){ p.s.insert(p.ima); p.ima++; } } else { p.an.emplace_back(m); int col = p.st.top(); while (col != m){ p.s.erase(col); p.st.pop(); col = p.st.top(); } } que.push(p); } } return ret; } //S_(m,1) としてありえるか bool chan(vector v){ int ma = 0, n = v.size(); for(auto& i : v){ ma = max(ma, i); if(i) i = 1; } return ma == count(v); } vector next(vector> &mat, vector &ima){ int n = ima.size(); vector ret(n, 0LL); rep(i, n) rep(j, n) (ret[i] += mat[i][j] * ima[j]) %= mod; return ret; } vector mnpoly(vector> &mnp, vector &truepoly){ int n = mnp.size(), m = truepoly.size(); vector ret(n, 0LL); rep(i, n) for(int j: truepoly) ret[i] += mnp[i][j]; return ret; } int main() { int m, n; cin >> m >> n; assert(n > 0 && n < 101 && m > 0 && m < 9); int ni = 1 << m; vector> ar(ni ,vector (m)); repp(i, ni, 1) rep(j, m){ if (i >> j & 1) ar[i][j] = 1; else ar[i][j] = 0; } vector > > col((m + 3) / 2); repp(i, (m + 3) / 2, 1) col[i] = komo(i); vector > ans; rep(i, ni){ int a = count(ar[i]); rep(j, col[a].size()){ auto b = ar[i]; ans.push_back(paint(b, col[a][j])); } } //the number of recurrence formulas int zen = ans.size(); map, int> mp; rep(i,zen) mp[ans[i]] = i; //recurrence matrix vector > mat(zen, vector (zen, 0LL)); vector tan(m, 0); rep(i, zen){ repp(j, ni, 1){ auto x = color(ans[i], ar[j]); if (x == tan) continue; int ind = mp[x]; mat[ind][i] += 1LL; } } vector> mnp(1, vector(zen)); rep(i, zen){ if (chan(ans[i])) mnp[0][i] = 1LL; else mnp[0][i] = 0LL; } rep(i, n){ auto a = mnp[i]; auto b = next(mat, a); mnp.push_back(b); } //連結なpolyominoのindex vector truepoly; rep(i, zen){ bool ok = true; rep(j, m) if(ans[i][j] > 1) ok = false; if (ok) truepoly.pb(i); } auto kai = mnpoly(mnp, truepoly); ll polysum = 0LL; rep(i, n) (polysum += ll(n - i) * kai[i]) %= mod; cout << polysum << endl; return 0; }