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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

%I

%S 1,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97,

%T 101,103,107,109,113,127,131,137,139,149,151,157,163,167,173,179,181,

%U 191,193,197,199,211,223,227,229,233,239,241,251,257,263,269,271,277,281,283,293

%N 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.

%C Contains the subsequence A066488 and differs therefore from A140475. [From _R. J. Mathar_, Aug 09 2010]

%H R. J. Mathar, <a href="/A175212/b175212.txt">Table of n, a(n) for n = 1..9970</a>

%e 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.

%Y Cf. A000975, A001045

%K easy,nonn

%O 1,2

%A _Ctibor O. Zizka_, Mar 06 2010

%E Term 34 removed, sequence extended and index in definition corrected by _R. J. Mathar_, Mar 29 2010

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Last modified February 29 09:41 EST 2020. Contains 332355 sequences. (Running on oeis4.)