A038224 Triangle whose (i,j)-th entry is binomial(i,j)*3^(i-j)*6^j.

1, 3, 6, 9, 36, 36, 27, 162, 324, 216, 81, 648, 1944, 2592, 1296, 243, 2430, 9720, 19440, 19440, 7776, 729, 8748, 43740, 116640, 174960, 139968, 46656, 2187, 30618, 183708, 612360, 1224720, 1469664, 979776, 279936, 6561, 104976

Offset

0,2

References

B. N. Cyvin et al., Isomer enumeration of unbranched catacondensed polygonal systems with pentagons and heptagons, Match, No. 34 (Oct 1996), pp. 109-121.

Links

Table of n, a(n) for n=0..37.

Example

1;
3,6;
9,36,36;
27,162,324,216;
81,648,1944,2592,1296;
243,2430,9720,19440,19440,7776;
729,8748,43740,116640,174960,139968,46656;
2187,30618,183708,612360,1224720,1469664,979776,279936;

Maple

A038224 := proc(n, k)
        if k < 0 or k > n then
                0;
        else
                binomial(n, k)*3^(n-k)*6^k ;
        end if;
end proc: # R. J. Mathar, Mar 26 2013

Mathematica

Table[Binomial[i, j]3^(i-j) 6^j, {i, 0, 10}, {j, 0, i}]//Flatten (* Harvey P. Dale, Feb 22 2020 *)

Crossrefs

Sequence in context: A195205 A045638 A305322 * A133195 A196156 A103978

Adjacent sequences: A038221 A038222 A038223 * A038225 A038226 A038227

Keyword

nonn,tabl,easy

Author

N. J. A. Sloane.

Status

approved