cp's OEIS Frontend

A030274 Numerators of sequence {b(1), b(2), ...} which when COMPOSED with itself gives {1,2,3,...}.

%I A030274 #27 Jan 13 2024 10:43:00
%S A030274 1,1,1,1,1,0,1,3,-29,25,263,-1481,-5493,80505,41549,-10584341,
%T A030274 14534299,431101045,-1767586509,-43076199745,322525095431,
%U A030274 1295531336537,-30908646610497,-734222129667169,13259294064756895,59705027567272273,-1617292893727823431,-1346735121534484263
%N A030274 Numerators of sequence {b(1), b(2), ...} which when COMPOSED with itself gives {1,2,3,...}.
%H A030274 Dmitry Kruchinin and Vladimir Kruchinin, <a href="http://arxiv.org/abs/1302.1986">Method for solving an iterative functional equation A^{2^n}(x)=F(x)</a>, arXiv:1302.1986 [math.CO], 2013.
%H A030274 N. J. A. Sloane, <a href="/transforms.txt">Transforms</a>
%F A030274 a(n) = numerator(T(n,1)), T(n,m) = (1/2)*(binomial(n+m-1,2*m-1) - sum(i=m+1..n-1, T(n,i)*T(i,m))), n > m, T(n,n)=1. - _Vladimir Kruchinin_, Mar 14 2012
%e A030274 1, 1, 1/2, 1/4, 1/8, 0, 1/16, 3/64, -29/128, 25/128, 263/256, -1481/512, -5493/1024, 80505/2048, ... = A030274/A030275
%t A030274 t[n_, m_] := t[n, m] = If[ n == m , 1 , 1/2*(Binomial[n+m-1, 2*m-1] - Sum[t[n, i]*t[i, m], {i, m+1, n-1}])]; a[n_] := t[n, 1] // Numerator; Table[a[n], {n, 1, 28}] (* _Jean-François Alcover_, Feb 26 2013, after _Vladimir Kruchinin_ *)
%o A030274 (Maxima)
%o A030274 T(n, m):=if n=m then 1 else 1/2*(binomial(n+m-1, 2*m-1)-sum(T(n, i)*T(i, m), i, m+1, n-1));
%o A030274 makelist(num(T(n, 1)), n, 1, 10); /* _Vladimir Kruchinin_, Mar 14 2012 */
%Y A030274 Cf. A030275, A091138.
%K A030274 sign,frac
%O A030274 1,8
%A A030274 _N. J. A. Sloane_
%E A030274 More terms from _Vladeta Jovovic_, Dec 19 2003