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%I #17 May 16 2019 18:39:39
%S 1,2,3,4,5,6,9,7,8,14,10,11,18,12,13,24,15,16,30,17,19,34,20,21,39,22,
%T 23,43,25,26,50,27,28,54,29,31,57,33,32,35,36,70,37,38,73,40,41,78,42,
%U 44,85,45,46,90,47,48,94,49,51,97,52,53,104,55,56,109,58,59,116,61,60,62,63
%N Absolute values of first differences of A081145.
%C The (signed) differences themselves are in A099004, but this sequence is important enough to have its own entry.
%C Conjectured (see the Slater-Velez and Velez articles) to be a permutation of the positive integers.
%C It appears that the terms line on two lines (this is true for the first million terms): see A308016-A308020.
%H Chai Wah Wu, <a href="/A308007/b308007.txt">Table of n, a(n) for n = 1..5000</a>
%H P. J. Slater and W. Y. Velez, <a href="http://projecteuclid.org/euclid.pjm/1102811644">Permutations of the Positive Integers with Restrictions on the Sequence of Differences</a>, Pacific Journal of Mathematics, Vol. 71, No. 1, 1977, 193-196.
%H P. J. Slater and W. Y. Velez, <a href="https://projecteuclid.org/euclid.pjm/1102784895">Permutations of the Positive Integers with Restrictions on the Sequence of Differences, II</a>, Pacific Journal of Mathematics, Vol. 82, No. 2, 1979, 527-531.
%H William Y. Velez, <a href="https://doi.org/10.1016/0012-365X(92)90724-T">Research problems 159-160</a>, Discrete Math., 110 (1992), pp. 301-302.
%Y Cf. A081145, A081146, A099004, A308021.
%Y See also A308016-A308020.
%K nonn
%O 1,2
%A _N. J. A. Sloane_, May 13 2019
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