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A206848 G.f.: exp( Sum_{n>=1} x^n/n * Sum_{k=0..n} binomial(n^2, k^2) ). 6
1, 2, 5, 53, 3422, 826606, 1335470713, 9548109569885, 190076214495558260, 18558289189760778318731, 10286810587274357297985552184, 16301371794177939084545371104827679, 91249944361047494534207504939405352235731, 3283593155431496336538359592977826684908598341441 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,2
COMMENTS
Logarithmic derivative yields A206849.
Equals row sums of triangle A228902.
LINKS
EXAMPLE
G.f.: A(x) = 1 + 2*x + 5*x^2 + 53*x^3 + 3422*x^4 + 826606*x^5 + 1335470713*x^6 +...
where the logarithm of the g.f. yields the l.g.f. of A206849:
log(A(x)) = 2*x + 6*x^2/2 + 137*x^3/3 + 13278*x^4/4 + 4098627*x^5/5 +...
PROG
(PARI) {a(n)=polcoeff(exp(sum(m=1, n, sum(k=0, m, binomial(m^2, k^2))*x^m/m)+x*O(x^n)), n)}
for(n=0, 25, print1(a(n), ", "))
CROSSREFS
Cf. variants: A167006, A228809.
Sequence in context: A330282 A071880 A071882 * A081482 A134475 A218030
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Feb 15 2012
STATUS
approved

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Last modified April 24 05:26 EDT 2024. Contains 371918 sequences. (Running on oeis4.)