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A278999 Numbers of the form (5h+2)*5^k-1 or (5h+3)*5^k-1 for h,k in N. 2

%I

%S 1,2,6,7,9,11,12,14,16,17,21,22,26,27,31,32,34,36,37,39,41,42,46,47,

%T 49,51,52,56,57,59,61,62,64,66,67,71,72,74,76,77,81,82,84,86,87,89,91,

%U 92,96,97,101,102,106,107,109,111,112,114,116,117,121,122,126,127,131

%N Numbers of the form (5h+2)*5^k-1 or (5h+3)*5^k-1 for h,k in N.

%H Ray Chandler, <a href="/A278999/b278999.txt">Table of n, a(n) for n = 1..10000</a>

%H Hao Fu, G.-N. Han, <a href="https://arxiv.org/abs/1601.04370">Computer assisted proof for Apwenian sequences related to Hankel determinants</a>, arXiv preprint arXiv:1601.04370 [math.NT], 2016. See sequence "K" in Section 2.2.

%t isok[n_]:=Module[{ord=IntegerExponent[n+1,5]},MemberQ[{2,3},Mod[(n+1)/5^ord,5]]];Select[Range[0,131],isok] (*_Ray Chandler_, Dec 17 2016*)

%Y Complement of A278998.

%K nonn

%O 1,2

%A _N. J. A. Sloane_, Dec 07 2016

%E More terms from _Ray Chandler_, Dec 17 2016

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Last modified June 21 19:59 EDT 2021. Contains 345365 sequences. (Running on oeis4.)