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 A237499 #19 Feb 01 2025 15:47:35 %S A237499 2,7,13,19,31,61,107,127,521,607,1279,3217,11213,21701,44497,132049, %T A237499 216091,756839,1257787,3021377,6972593,20996011,24036583,30402457, %U A237499 37156667,43112609,82589933 %N A237499 Odious Mersenne exponents. %t A237499 Select[MersennePrimeExponent[Range[47]], OddQ @ DigitCount[#, 2][[1]] &] (* _Amiram Eldar_, Dec 10 2019 *) %Y A237499 Intersection of A000043 and A027697. %Y A237499 Cf. A000069, A174265. %K A237499 nonn,base,more %O A237499 1,1 %A A237499 _Ilya Lopatin_ and _Juri-Stepan Gerasimov_, Feb 08 2014 %E A237499 a(13) and a(18) inserted and more terms added by _Amiram Eldar_, Dec 10 2019 %E A237499 a(27) added by _Harvey P. Dale_, Feb 01 2025