A255928 Expansion of exp( Sum_{n >= 1} A094088(n)*x^n/n ).

1, 1, 4, 44, 1025, 41693, 2617128, 234091692, 28251572652, 4421489003700, 870650503128708, 210629395976568828, 61405707768736724472, 21231253444779700476672, 8589776776743377081599500, 4020181599664131540547091076, 2155088041310451318611119556661

Offset

0,3

Comments

It appears that this sequence is integer valued.

The o.g.f. A(x) = 1 + x + 4*x^2 + 44*x^3 + ... for this sequence is such that 1 + x*d/dx( log(A(x) ) is the o.g.f. for A094088.

This sequence is the particular case m = 1 of the following general conjecture.

Let m be an integer and consider the sequence u(n) defined by the recurrence u(n) = m*Sum_{k = 0..n-1} binomial(2*n,2*k) *u(k) with the initial condition u(0) = 1. Then the expansion of exp( Sum_{n >= 1} u(n)*x^n/n ) ) has integer coefficients.

For cases see A255926(m = -3), A255882(m = -2), A255881(m = -1), A255929(m = 2) and A255930(m = 3).

Note that u(n), as a polynomial in the variable m, is the n-th row generating polynomial of A241171.

Links

Table of n, a(n) for n=0..16.

Formula

O.g.f.: exp(x + 7*x^2/2 + 121*x^3/3 + 3907*x^4/4 + ...) = 1 + x + 4*x^2 + 44*x^3 + 1025*x^4 + ....

a(0) = 1 and a(n) = 1/n*Sum_{k = 0..n-1} A094088(n-k)*a(k) for n >= 1.

Maple

#A255928
A094088 := proc (n) option remember; if n = 0 then 1 else add(binomial(2*n, 2*k)*A094088(k), k = 0 .. n-1) end if; end proc:
A255928 := proc (n) option remember; if n = 0 then 1 else add(A094088(n-k)*A255928(k), k = 0 .. n-1)/n end if; end proc:
seq(A255928(n), n = 0 .. 16);

Crossrefs

Cf. A094088, A241171, A255926(m = -3), A255882(m = -2), A255881(m = -1), A255929(m = 2), A255930(m = 3).

Sequence in context: A374279 A301942 A348130 * A137783 A136552 A155556

Adjacent sequences: A255925 A255926 A255927 * A255929 A255930 A255931

Keyword

nonn,easy

Author

Peter Bala, Mar 11 2015

Status

approved