1,1

Intersection of A045619 and A073491; A000142 is a subsequence apart from initial terms.

Table of n, a(n) for n=1..41.

a(10) = 210 = 2 * 3 * 5 * 7 = 5 * (5+1) * (5+2);

a(11) = 240 = 2^4 * 3 * 5 = 15 * (15+1);

a(12) = 360 = 2^3 * 3^2 * 5 = 3 * (3+1) * (3+2) * (3+3);

a(13) = 420 = 2^2 * 3 * 5 * 7 = 20 * (20+1);

a(14) = 600 = 2^3 * 3 * 5^2 = 24 * (24+1);

a(15) = 720 = 2^4 * 3^2 * 5 = 6!.

Sequence in context: A244043 A058868 A129314 * A194096 A099993 A011778

Adjacent sequences: A137892 A137893 A137894 * A137896 A137897 A137898

nonn

Reinhard Zumkeller, Feb 20 2008

approved