A065917 Boundaries of primorial intervals [1,3]; [3,9],[9,15]; [15,45], etc.

1, 3, 9, 15, 45, 75, 105, 315, 525, 735, 945, 1155, 3465, 5775, 8085, 10395, 12705, 15015, 45045, 75075, 105105, 135135, 165165, 195195, 225225, 255255, 765765, 1276275, 1786785, 2297295, 2807805, 3318315, 3828825, 4339335, 4849845

Offset

1,2

Links

Table of n, a(n) for n=1..35.

Formula

a(n+1)= a(n)+q(j) for primorial q(j) < a(n+1) <= q(j+1)/2.

Example

a(4)= 15= a(3)+q(2)= 9+ 6, a(7)= 105= a(6)+q(3)= 75+ 30,
a(5)= 45= a(4)+q(3)=15+30, a(8)= 315= a(7)+q(4)=105+210.

Crossrefs

Primorial q(j)= A002110(j), interval count A005521(j+1)-1.

Sequence in context: A345431 A082702 A214771 * A355772 A355771 A053624

Adjacent sequences: A065914 A065915 A065916 * A065918 A065919 A065920

Keyword

nonn,easy

Author

Frank Ellermann, Dec 08 2001

Status

approved