A132841 - OEIS

%I #2 Mar 30 2012 18:37:05

%S 1,3,4,7,11,12,15,23,31,33,34,40,53,59,74,87,103,111,115,117,123,124,

%T 139,152,161,185,193,203,204,222,249,279,301,309,340,355,371,383,407,

%U 413,452,467,474,480,506,509,518,552,554,583,616,657,690,705,759,779

%N Least increasing logarithmic coefficients such that exponentiation results in an integer sequence (A132842), starting with a(1)=1.

%e L.g.f.: A(x) = x + 3x^2/2 + 4x^3/3 + 7x^4/4 + 11x^5/5 + 12x^6/6 + 15x^7/7 +...

%e exp(A(x)) = 1 + x + 2x^2 + 3x^3 + 5x^4 + 8x^5 + 12x^6 + 18x^7 +...(A132842).

%o (PARI) {a(n)=local(A,t,r=1);A=if(n==1,[1],vector(n-1,j,a(j)/j));if(n==1,r=1, for(j=1,n,if(denominator(Vec(exp(x*Ser(concat(A,(a(n-1)+j)/n))))[n+1])==1, r=a(n-1)+j;j=n+1)));r}

%Y Cf. A132842.

%K nonn

%O 1,2

%A _Paul D. Hanna_, Sep 12 2007