The On-Line Encyclopedia of Integer Sequences (OEIS)

A216688 revision #18

A216688

E.g.f. exp( x * exp(x^2) ).

1, 1, 1, 7, 25, 121, 841, 4831, 40657, 325585, 2913841, 29910871, 301088041, 3532945417, 41595396025, 531109561711, 7197739614241, 100211165640481, 1507837436365537, 23123578483200295, 376697477235716281, 6348741961892933401, 111057167658053740201, 2032230051717594032767

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OFFSET

0,4

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..200

FORMULA

a(n)=(n!*sum(m=floor((n+1)/2)..n, ((2*m-n)^(n-m))/((2*m-n)!*(n-m)!))). [Vladimir Kruchinin, Mar 09 2013]]

MATHEMATICA

With[{nn = 25}, CoefficientList[Series[Exp[x Exp[x^2]], {x, 0, nn}],

x] Range[0, nn]!] (* Bruno Berselli, Sep 14 2012 *)

PROG

(PARI)

x='x+O('x^66);

Vec(serlaplace(exp( x * exp(x^2) )))

/* Joerg Arndt, Sep 14 2012 */

CROSSREFS

Cf. A216507 (e.g.f. exp(x^2*exp(x)), A216689 (e.g.f. exp(x*exp(x)^2)).

Cf. A000248 (e.g.f. exp(x*exp(x))), A003725 (e.g.f. exp(x*exp(-x))).

Sequence in context: A266810 A199893 A129791 * A141626 A138292 A138738

Adjacent sequences: A216685 A216686 A216687 * A216689 A216690 A216691

KEYWORD

nonn,changed

AUTHOR

Joerg Arndt, Sep 14 2012

STATUS

editing