A121007 Denominators of partial alternating sums of Catalan numbers scaled by powers of 1/5.

1, 5, 25, 25, 625, 3125, 15625, 78125, 78125, 1953125, 9765625, 48828125, 244140625, 244140625, 1220703125, 6103515625, 30517578125, 152587890625, 30517578125, 3814697265625, 19073486328125

Offset: 0

Author

Wolfdieter Lang, Aug 16 2006

Keywords

• nonn
• frac
• easy

Comments

Numerators are given under A121006. See A121006 for further comments.

Examples

			Rationals r(n): 1, 4/5, 22/25, 21/25, 539/625, 2653/3125, 13397/15625, 66556/78125, 66842/78125, 1666188/1953125, 8347736/9765625,...
		

Crossrefs

The second member (p=2) is A121008/A121009.

Formula

a(n)=denominator(r(n)) with r(n) := rIII(p=1,n) = sum(((-1)^k)*C(k)/5^k,k=0..n) and C(k):=A000108(k) (Catalan). The rationals r(n) are given in lowest terms.