The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A141120 G.f. A(x) satisfies: A(A(A(A(A(x))))) = x + 25*x^2. 4
 1, 5, -100, 3250, -127500, 5456250, -241875000, 10733906250, -463469531250, 18897269531250, -699306093750000, 21927485449218750, -487263216796875000, 923644008789062500, 602420821142578125000, -38171197412384033203125 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Robert Israel, Table of n, a(n) for n = 1..128 EXAMPLE G.f.: A(x) = x + 5*x^2 - 100*x^3 + 3250*x^4 - 127500*x^5 +5456250*x^6+... A(A(x)) = x + 10*x^2 - 150*x^3 + 4125*x^4 - 140000*x^5 +5162500*x^6+... A(A(A(x))) = x + 15*x^2 - 150*x^3 + 3375*x^4 - 96250*x^5 +2931250*x^6+... A(A(A(A(x)))) = x + 20*x^2 - 100*x^3 + 1750*x^4 - 40000*x^5 +918750*x^6+.. MAPLE X[1]:= unapply(x+c[2]*x^2, x): for i from 2 to 6 do   S:= series((X[i-1]@@5)(x)-x-25*x^2, x, 2^(i-1)+1);   Sol:=solve({seq(coeff(S, x, k), k=2^(i-2)+1..2^(i-1))}, {seq(c[k], k=2^(i-2)+1 ..2^(i-1))});   X[i]:= unapply(subs(Sol, X[i-1](x))+add(c[j]*x^j, j=2^(i-1)+1..2^(i)), x); od: seq(coeff(X[i](x), x, i), i=1..2^5)); # Robert Israel, Jul 20 2020 PROG (PARI) {a(n, m=5)=local(F=x+m*x^2+x*O(x^n), G); if(n<1, 0, for(k=3, n, G=F+x*O(x^k); for(i=1, m-1, G=subst(F, x, G)); F=F+((-polcoeff(G, k))/m)*x^k); return(polcoeff(F, n, x)))} CROSSREFS Cf. A027436, A141118, A141119, A141121. Sequence in context: A208348 A128784 A078534 * A123668 A336427 A197200 Adjacent sequences:  A141117 A141118 A141119 * A141121 A141122 A141123 KEYWORD sign AUTHOR Paul D. Hanna, Jun 05 2008 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified August 8 06:27 EDT 2020. Contains 336290 sequences. (Running on oeis4.)