The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A076176 a(n) = n!*sum( i+j<=n, 1/i!/j! ) for 0 <= i <= j < n. 2
 1, 2, 7, 25, 111, 571, 3468, 24340, 194883, 1754203, 17542668, 192970372, 2315646974, 30103414758, 421447816520, 6321717264184, 101147476266147, 1719507096590035, 30951127738776012, 588071427037006372 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..200 FORMULA E.g.f.: (exp(2*x)+I_0(2*x))/(2-2*x). Recurrence: n*a(n) = (n^2 + 2*n - 2)*a(n-1) - 2*(n-3)*(n-1)*a(n-2) - 4*(n-2)*(n+1)*a(n-3) + 8*(n-3)*(n-2)*a(n-4). - Vaclav Kotesovec, Feb 25 2014 a(n) ~ c * n!, where c = (exp(2) + BesselI(0,2)) / 2 = 4.83432070063335874733381595... - Vaclav Kotesovec, Feb 25 2014 MATHEMATICA Table[n!*Sum[Boole[i+j <= n]/(i!*j!), {i, 0, n}, {j, i, n}], {n, 0, 20}] (* Vaclav Kotesovec, Feb 25 2014 *) PROG (PARI) a(n)=if(n<0, 0, n!*sum(i=0, n, sum(j=i, n-i, 1/i!/j!))) (PARI) a(n)=if(n<0, 0, n!*polcoeff((exp(2*x+x*O(x^n))+besseli(0, 2*x+x*O(x^n)))/(2-2*x), n)) CROSSREFS Cf. A076177. Sequence in context: A150533 A150534 A150535 * A188719 A103465 A103464 Adjacent sequences: A076173 A076174 A076175 * A076177 A076178 A076179 KEYWORD nonn AUTHOR Benoit Cloitre, Nov 01 2002 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified August 5 11:26 EDT 2024. Contains 374950 sequences. (Running on oeis4.)