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A026127 a(n) = T(2n-1,n-1), where T is the array in A026120. 2
1, 4, 20, 110, 608, 3409, 19304, 110187, 632960, 3654915, 21195716, 123365099, 720240584, 4216176575, 24738092400, 145444454754, 856662911136, 5053815390148, 29857490333880, 176624209891024 (list; graph; refs; listen; history; internal format)
OFFSET

1,2

PROG

PARI programs from R. J. Mathar:

A026300(n, k)={ if(n<0 || k < 0, return(0) ; ) ; if(n<=1, 1, if(k==0, 1, if(k<n, A026300(n-1, k-2)+A026300(n-1, k-1)+A026300(n-1, k), A026300(n-1, n-2)+A026300(n-1, n-1)) ; ) ; ) ; }

A026300(n, k)={ if(n<0 || k < 0, return(0) ; ) ; if(n<=1, 1, if(k==0, 1, sum(i=0, k/2, binomial(n, 2*i+n-k)*(binomial(2*i+n-k, i)-binomial(2*i+n-k, i-1))) ; ) ; ) ; }

A026105(n, k)={ if(k==0 || n<=1, 1, A026300(n, k)-A026300(n-1, k-1) ; ) ; }

A026120(n, k)={ if(n<=1, if(k== -1 || k < n, 1, 0), A026105(n+1, k+1)-A026105(n, k) ; ) ; }

A026127(n)={ A026120(2*n-1, n-1) ; } { /* test for(i=0, 7, for(j=0, i, print(A026300(i, j))) ; print("; ") ; ) ; */ /* test for(i=-1, 7, for(j=-1, i, print(A026120(i, j))) ; print("; ") ; ) ; */ for(n=1, 20, print(n, " ", A026127(n))) ; }

CROSSREFS

Sequence in context: A135159 A190724 A020084 * A153295 A006770 A158827

Adjacent sequences:  A026124 A026125 A026126 * A026128 A026129 A026130

KEYWORD

nonn

AUTHOR

Clark Kimberling (ck6(AT)evansville.edu)

EXTENSIONS

Corrected by R. J. Mathar, Oct 26 2006

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Last modified February 17 06:27 EST 2012. Contains 205998 sequences.