login
G.f.: A(x) = exp( Sum_{n>=1} A000172(n^2)*x^n/n ) where Franel number A000172(n) = Sum_{k=0..n} C(n,k)^3.
4

%I #7 Jan 01 2025 15:40:55

%S 1,2,175,1760658,1583078442003,109611485085305859618,

%T 547114144500297420116784959134,

%U 189879050147329004652707990280499398833960,4482752989702739533106941067588051779825642693578987967,7097288803262045586874332782527584396862908242415791224663533782367102

%N G.f.: A(x) = exp( Sum_{n>=1} A000172(n^2)*x^n/n ) where Franel number A000172(n) = Sum_{k=0..n} C(n,k)^3.

%e G.f.: A(x) = 1 + 2*x + 175*x^2 + 1760658*x^3 + 1583078442003*x^4 +...

%e where

%e log(A(x)) = 2*x + 346*x^2/2 + 5280932*x^3/3 + 6332299624282*x^4/4 + 548057409594239814752*x^5/5 +...+ A000172(n^2)*x^n/n +...

%o (PARI) {a(n)=local(A=1+x); for(i=1, n, A=exp(sum(m=1, n, sum(j=0, m^2, binomial(m^2, j)^3)*x^m/m+x*O(x^n)))); polcoeff(A, n)}

%o for(n=0, 31, print1(a(n), ", "))

%Y Cf. A216356, A166990, A216352, A216353, A216354, A000172.

%K nonn

%O 0,2

%A _Paul D. Hanna_, Sep 04 2012