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1, 2, 4, 10, 32, 130, 652, 3914, 27400, 219202, 1972820, 19728202, 217010224, 2604122690, 33853594972, 473950329610, 7109254944152, 113748079106434, 1933717344809380, 34806912206568842, 661331331924808000, 13226626638496160002
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| Row sums of A094816 as a triangular array as follows : {1}, {1, 1}, {1, 3}, {1, 1, 8}, {6, 1, 1, 24}, {29, 10, 1, 1, 89}, ... - Michael Somos Nov 19 2006
a(n) =(n-1)a(n-1)+2,n>0...2=0*1+2, 4=1*2+2,10=2*4+2... [From Gary Detlefs (gdetlefs(AT)aol.com), May 20 2010]
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FORMULA
| a(n+1)=Sum(2*n!/j!,j=0..n). - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Oct 20 2006
a(n)= 2*floor(e*(n-1)!),n>1 [From Gary Detlefs (gdetlefs(AT)aol.com), May 20 2010]
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MAPLE
| a:=n->sum(2*(n-1)!/j!, j=0..n-1): seq(a(n), n=1..18); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Oct 20 2006
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PROG
| (PARI) {a(n)= local(A); if(n<1, n==0, A=vector(n); A[1]=2; for(k=1, n-1, A[k+1]=k*A[k]+2); A[n])} /* Michael Somos Nov 19 2006 */
(PARI) {a(n)= if(n<1, n==0, n--; n!*polcoeff( 2*exp(x+x*O(x^n))/(1-x), n))} /* Michael Somos Nov 19 2006 */
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CROSSREFS
| a(n+1)=2*A000522(n).
Sequence in context: A009284 A105557 A166741 * A056593 A154219 A173489
Adjacent sequences: A054088 A054089 A054090 * A054092 A054093 A054094
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KEYWORD
| nonn
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AUTHOR
| Clark Kimberling (ck6(AT)evansville.edu)
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