A175212 Numbers n such that A000975(n-1)/n is an integer. Also numbers n such that arithmetic mean of the first n Jacobsthal numbers is an integer.

1, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293

Offset: 1

Author

Ctibor O. Zizka, Mar 06 2010

Keywords

• easy
• nonn

Comments

Contains the subsequence A066488 and differs therefore from A140475. [From R. J. Mathar, Aug 09 2010]

Examples

			Arithmetic mean of partial sums of Jacobsthal numbers is an integer : 0/1=0 n=1; (0+1+1+3+5)/5=2 n=5; (0+1+1+3+5+11+21)/7=6 n=7; (0+1+1+3+5+11+21+43+85+171+341)/11=62 n=11 etc.
		

Links

• R. J. Mathar, Table of n, a(n) for n = 1..9970

Crossrefs

Cf. A000975, A001045

Extensions

Term 34 removed, sequence extended and index in definition corrected by R. J. Mathar, Mar 29 2010