A217920 Column 1 of A217916 (when formed into a number triangle).

2, 1, 2, 4, 2, 6, 6, 2, 6, 2, 6, 14, 4, 12, 6, 2, 4, 4, 2, 2, 6, 6, 2, 4, 6, 8, 6, 16, 6, 4, 6, 6, 6, 6, 6, 6, 14, 6, 6, 14, 10, 10, 8, 4, 12, 20, 8, 12, 6, 10, 2, 6, 14, 2, 14, 18, 6, 2, 6, 12, 4, 28, 6, 20, 6, 6, 6, 4, 16, 2, 2, 6, 4, 12, 6, 6, 6, 6, 8, 4, 6, 8, 6

Offset: 1

Author

Paul D. Hanna, Mar 04 2013

Keywords

• nonn

Comments

The number 2 appears in A217916 only in column 1.

The positions of 2 are given by A217919.

Links

• Paul D. Hanna, Table of n, a(n) for n = 1..287

Crossrefs

Cf. A217916, A217918, A217919.

Formula

a(n) = prime(n*(n-1)/2 + 1) - prime(n*(n-1)/2) for n>1 with a(1)=2.