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 A206581 #12 May 15 2025 08:18:30 %S A206581 5,11,13,19,23,37,43,47,61,67,73,79,103,151,157,163,191,193,211,223, %T A206581 271,277,283,313,331,367,383,397,421,457,463,487,523,541,547,607,613, %U A206581 631,661,673,691,733,751,757,787,823,877,907,991,997,1051,1087,1093 %N A206581 Odd primes p such that p+1 is a prime times a power of two. %C A206581 Very similar to A192869; here p+1 = q*2^k, where q must be prime. %H A206581 T. D. Noe, <a href="/A206581/b206581.txt">Table of n, a(n) for n = 1..1000</a> %H A206581 Kevin Broughan and Zhou Qizhi, <a href="https://doi.org/10.1017/S0004972710000067">Flat primes and thin primes</a>, Bulletin of the Australian Mathematical Society 82:2 (2010), pp. 282-292. %F A206581 a(n) >> n log^2 n is implicit in Broughan & Qizhi, see A192869. - _Charles R Greathouse IV_, Sep 15 2015 %t A206581 Select[Prime[Range[2, 1000]], PrimeQ[(#+1)/2^IntegerExponent[#+1, 2]] &] %o A206581 (PARI) is(n)=isprime(n) && n>4 && isprime((n+1)>>valuation(n+1,2)) \\ _Charles R Greathouse IV_, Sep 15 2015 %Y A206581 Subsequence of A192869. %K A206581 nonn %O A206581 1,1 %A A206581 _T. D. Noe_, Mar 07 2012