A172522 Partial sums of A049094.

6, 18, 36, 56, 77, 101, 131, 167, 207, 249, 297, 351, 411, 474, 540, 612, 690, 770, 854, 944, 1040, 1140, 1242, 1347, 1455, 1565, 1679, 1799, 1925, 2057, 2193, 2331, 2471, 2615, 2762, 2912, 3067, 3223, 3383, 3545, 3713, 3887, 4067, 4253, 4442, 4634, 4832

Offset: 1

Author

Jonathan Vos Post, Feb 06 2010

Keywords

• nonn

Comments

The subsequence of primes in this sequence begins: 101, 131, 167, 3067.

Examples

			a(20) = 6 + 12 + 18 + 20 + 21 + 24 + 30 + 36 + 40 + 42 + 48 + 54 + 60 + 63 + 66 + 72 + 78 + 80 + 84 + 90.
		

Crossrefs

Cf. A000040, A014491, A049093, A049096, A049095, A001220.

Formula

a(n) = SUM[i=1..n] {i such that 2^i - 1 is divisible by a square}.

Extensions

More terms from R. J. Mathar, Feb 16 2010