A138738 E.g.f. satisfies: A(x) = exp(x*exp(x^2*exp(x^3*exp(...exp(x^n*...))))).

1, 1, 1, 7, 25, 121, 1561, 9871, 101137, 1293265, 15765841, 226501111, 3355388521, 55348183177, 981791212585, 19611613003711, 387083895223201, 8241127257050401, 193814428658623777, 4572332597344204135, 116627907470591924281, 3142752742361513926681

Offset

0,4

Comments

a(n) == 1 (mod 6) (conjecture).

Links

Paul D. Hanna, Table of n, a(n) for n = 0..400

Example

E.g.f: A(x) = 1 + x + 1/2*x^2 + 7/6*x^3 + 25/24*x^4 + 121/120*x^5 +...

Prog

(PARI) {a(n)=local(A=1); for(i=0, n-1, A=exp(x^(n-i)*A+x*O(x^n))); n!*polcoeff(A, n)}
for(n=0, 30, print1(a(n), ", "))

Crossrefs

Cf. A138292.

Sequence in context: A216688 A141626 A138292 * A057573 A082651 A241714

Adjacent sequences: A138735 A138736 A138737 * A138739 A138740 A138741

Keyword

nonn

Author

Paul D. Hanna, Mar 27 2008

Status

approved