This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A088713 #19 Jan 15 2018 08:52:24 %S A088713 1,1,2,6,24,118,674,4308,30062,225266,1791964,15009118,131566314, %T A088713 1201452248,11389283418,111761444078,1132680800640,11834071103246, %U A088713 127261591139010,1406778021294220,15967144849210158,185897394076705298 %N A088713 G.f. A(x) satisfies A(x/A(x)) = 1/(1-x). %H A088713 Vaclav Kotesovec, <a href="/A088713/b088713.txt">Table of n, a(n) for n = 0..300</a> %F A088713 G.f. satisfies: A(x) = 1 + x*A(x)*A(1-1/A(x)). %F A088713 G.f.: A(x*g(x)) = g(x) = (1-1/A(x))/x where g(x) is the g.f. of A088714. %F A088713 From _Paul D. Hanna_, Dec 06 2009: (Start) %F A088713 G.f. satisfies: A(x) = 1 + A(x)*Series_Reversion(x/A(x)). %F A088713 G.f. satisfies: A( (x/(1+x)) / A(x/(1+x)) ) = 1 + x. %F A088713 (End) %F A088713 Logarithmic derivative: given g.f. A(x), let G(x) = A(x*G(x)) be the g.f. of A088714, then A'(x)/A(x) = (G(x) + x*G'(x)) / (1 - x*G(x)). %e A088713 G.f.: A(x) = 1 + x + 2*x^2 + 6*x^3 + 24*x^4 + 118*x^5 + 674*x^6 +... %e A088713 Illustration of logarithmic derivation. %e A088713 If we form an array of coefficients of x^k in A(x)^n, n>=1, like so: %e A088713 A^1: [1],1, 2, 6, 24, 118, 674, 4308, ...; %e A088713 A^2: [1, 2], 5, 16, 64, 308, 1716, 10724, ...; %e A088713 A^3: [1, 3, 9], 31, 126, 600, 3278, 20070, ...; %e A088713 A^4: [1, 4, 14, 52], 217, 1032, 5560, 33440, ...; %e A088713 A^5: [1, 5, 20, 80, 345], 1651, 8820, 52270, ...; %e A088713 A^6: [1, 6, 27, 116, 519, 2514],13385, 78420, ...; %e A088713 A^7: [1, 7, 35, 161, 749, 3689, 19663], 114269, ...; ... %e A088713 then the sums of the coefficients of x^k, k=0..n-1, in A(x)^n (shown above in brackets) begin: %e A088713 1 = 1; %e A088713 1 + 2 = 3; %e A088713 1 + 3 + 9 = 13; %e A088713 1 + 4 + 14 + 52 = 71; %e A088713 1 + 5 + 20 + 80 + 345 = 451; %e A088713 1 + 6 + 27 + 116 + 519 + 2514 = 3183; %e A088713 1 + 7 + 35 + 161 + 749 + 3689 + 19663 = 24305; ... %e A088713 and equal the coefficients in log(A(x)): %e A088713 log(A(x)) = x + 3*x^2/2 + 13*x^3/3 + 71*x^4/4 + 451*x^5/5 + 3183*x^6/6 + 24305*x^7/7 + 197551*x^8/8 +... %e A088713 The main diagonal in the above table forms the g.f. G(x) of A088714: %e A088713 [1/1, 2/2, 9/3, 52/4, 345/5, 2514/6, 19663/7, ...] %e A088713 where G(x) = 1 + x + 3*x^2 + 13*x^3 + 69*x^4 + 419*x^5 + 2809*x^6 +... %e A088713 satisfies A'(x)/A(x) = (G(x) + x*G'(x)) / (1 - x*G(x)). %t A088713 terms = 22; A[_] = 1; Do[A[x_] = 1 + x*A[x]*A[1 - 1/A[x]] + O[x]^j // Normal, {j, terms}]; CoefficientList[A[x], x] (* _Jean-François Alcover_, Jan 15 2018 *) %o A088713 (PARI) a(n)=local(A=1+x);for(i=1,n,A=(1+A*serreverse(x/(A+x*O(x^n))))^1);polcoeff(A,n) %o A088713 for(n=0,30,print1(a(n),", ")) \\ _Paul D. Hanna_, Dec 06 2009 %o A088713 (PARI) {a(n)=local(A=1+x);if(n==0,1,for(i=1,n, %o A088713 A=1+x*exp(sum(k=1,n-1,sum(j=0,k,polcoeff(A^k+x*O(x^j),j))*x^k/k)+x*O(x^n)))); %o A088713 polcoeff(A+x*O(x^n),n)} %o A088713 for(n=0,30,print1(a(n),", ")) \\ _Paul D. Hanna_, Dec 09 2013 %Y A088713 Cf. A088714. %Y A088713 Variants: A154677, A168448, A168449, A168478, A168479. %K A088713 nonn %O A088713 0,3 %A A088713 _Paul D. Hanna_, Oct 12 2003