A090220 Denominators used in A090219 to compute formula for column sequences of array A078741.

1, 1, 1, 1, 2, 10, 20, 70, 560, 1680, 2800, 30800, 369600, 800800, 11211200, 168168000, 448448000, 7623616000, 137225088000, 434546112000, 8690922240000, 182509367040000, 669201012480000, 15391623287040000, 369398958888960000

Offset

1,5

Comments

The corresponding numerator sequence is N(n) := [1, 6, 3, 1, 3, 3, 1, 3, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1] for n=1..26.

Links

Table of n, a(n) for n=1..25.

Formula

a(n) = lcm(seq(denominator(a(n+2, m))), m=1..n)), with the a(n, m) formula of A090219(n, m) but without the 1/b(n-2) factor and lcm denotes the least common multiple of a set of numbers.

N(n) := gcd(seq(numerator(a(n+2, m))), m=1..n)), with the a(n, m) formula of A090219(n, m) but without the 1/b(n-2) factor and gcd denotes the greatest common divisor > 1 of a set of numbers.

Example

The fifth (k=7) column of A078741 needs in A090219 the factor b(5) := N(5)/a(5)= 3/2.

Crossrefs

Sequence in context: A285104 A332393 A120552 * A164882 A029994 A298411

Adjacent sequences: A090217 A090218 A090219 * A090221 A090222 A090223

Keyword

nonn,easy

Author

Wolfdieter Lang, Dec 01 2003

Status

approved