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A278998 Numbers of the form (5h+1)*5^k-1 or (5h+4)*5^k-1 for h,k in N. 2

%I

%S 0,3,4,5,8,10,13,15,18,19,20,23,24,25,28,29,30,33,35,38,40,43,44,45,

%T 48,50,53,54,55,58,60,63,65,68,69,70,73,75,78,79,80,83,85,88,90,93,94,

%U 95,98,99,100,103,104,105,108,110,113,115,118,119,120,123,124,125,128,129,130

%N Numbers of the form (5h+1)*5^k-1 or (5h+4)*5^k-1 for h,k in N.

%H Ray Chandler, <a href="/A278998/b278998.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 "J" in Section 2.2.

%t isok[n_]:=Module[{ord=IntegerExponent[n+1,5]},MemberQ[{1,4},Mod[(n+1)/5^ord,5]]];Select[Range[0,131],isok] (*_Ray Chandler_, Dec 17 2016*)

%Y Complement of A278999.

%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 August 1 00:13 EDT 2021. Contains 346377 sequences. (Running on oeis4.)