This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A192864 #12 Sep 01 2020 08:55:35 %S A192864 3,5,7,11,13,17,23,29,31,41,43,47,53,59,61,67,71,79,83,89,97,103,107, %T A192864 113,131,137,139,149,157,167,173,179,191,193,211,223,227,229,233,239, %U A192864 241,257,263,269,277,281,283,293,311,313,317,331,337,347,349,353,359 %N A192864 Lower flat primes: odd primes p such that p-1 is a squarefree number times a power of two. %C A192864 Broughan & Qizhi show that this sequence has relative density 2*A in the primes, where A = A005596 is Artin's constant. Consequently, there exists a flat number between x and (1+e)x for every e > 0 and large enough x. %H A192864 Amiram Eldar, <a href="/A192864/b192864.txt">Table of n, a(n) for n = 1..10000</a> %H A192864 Kevin A. Broughan and Zhou Qizhi, <a href="https://doi.org/10.1017/S0004972710000067">Flat primes and thin primes</a>, Bulletin of the Australian Mathematical Society, Vol. 82, No. 2 (2010), pp. 282-292, <a href="http://www.math.waikato.ac.nz/~kab/papers/flatandthin4.pdf">alternative link</a>. %F A192864 a(n) ~ k * n * log(n) with k = 1/(2*A) = 1.3370563... %t A192864 Select[Range[3, 360, 2], PrimeQ[#] && SquareFreeQ[(# - 1)/2^IntegerExponent[# - 1, 2]] &] (* _Amiram Eldar_, Aug 30 2020 *) %o A192864 (PARI) is(n)=n%2&&isprime(n)&&issquarefree((n-1)>>valuation(n-1,2)) \\ corrected by _Amiram Eldar_, Aug 30 2020 %Y A192864 Subsequence of A192863. %Y A192864 Cf. A192861, A192862, A005596. %K A192864 nonn %O A192864 1,1 %A A192864 _Charles R Greathouse IV_, Jul 11 2011 %E A192864 Data corrected by _Amiram Eldar_, Aug 30 2020