A138776 Triangle read by rows: T(n,k)=binomial(n-2k,3k+1) (n>=1, 0<=k<=(n-1)/5).

1, 2, 3, 4, 5, 6, 1, 7, 5, 8, 15, 9, 35, 10, 70, 11, 126, 1, 12, 210, 8, 13, 330, 36, 14, 495, 120, 15, 715, 330, 16, 1001, 792, 1, 17, 1365, 1716, 11, 18, 1820, 3432, 66, 19, 2380, 6435, 286, 20, 3060, 11440, 1001

Offset

1,2

Comments

Row n contains floor((n+4)/5) terms.

Row sums yield A137357.

References

D. E. Knuth, The Art of Computer Programming, Vol. 4A, Section 7.1.4.

Links

Table of n, a(n) for n=1..50.

Maple

T:=proc(n, k) options operator, arrow: binomial(n-2*k, 3*k+1) end proc: for n to 20 do seq(T(n, k), k=0..(n-1)*1/5) end do; # yields sequence in triangular form

Mathematica

Table[Binomial[n-2k, 3k+1], {n, 30}, {k, 0, (n-1)/5}]//Flatten (* Harvey P. Dale, Aug 12 2018 *)

Crossrefs

Cf. A137357.

Sequence in context: A319092 A243733 A334618 * A339738 A364500 A280701

Adjacent sequences: A138773 A138774 A138775 * A138777 A138778 A138779

Keyword

nonn,tabf

Author

Emeric Deutsch, May 10 2008

Status

approved