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 A060286 #31 Jan 05 2025 18:03:29
%S A060286 6,28,496,8128,2096128,33550336,8589869056,137438691328,
%T A060286 35184367894528,144115187807420416,2305843008139952128,
%U A060286 9444732965670570950656,2417851639228158837784576,38685626227663735544086528,9903520314282971830448816128,40564819207303336344294875201536
%N A060286 a(n) = 2^(p-1)*(2^p-1) where p is prime(n).
%C A060286 a(n) is the number whose binary representation is p 1's together with p-1 0's, where p is prime(n), for example: prime(3) = 5 so a(3) = 496 = 111110000 (2). - _Omar E. Pol_, Dec 12 2012
%D A060286 C. Stanley Ogilvy and John T. Anderson, "Excursions in Number Theory", Oxford University Press, NY, 1966 pp. 20-23.
%H A060286 Harry J. Smith, <a href="/A060286/b060286.txt">Table of n, a(n) for n = 1..100</a>
%F A060286 For n > 1, a(2n) = 9*T(k) + 1 ; a(2n+1) = 9*T(K) + 1, where T(n) = A000217(n), k = (A121290(n) - 1)/2, K = 2*A121290(n). - _Lekraj Beedassy_, Sep 12 2006
%F A060286 a(A016027(n)) = A000396(n), assuming there are no odd perfect numbers. - _Omar E. Pol_, Dec 13 2012
%e A060286 a(4) = 2^6(2^7 - 1) = 8128.
%t A060286 Table[2^(Prime[n] - 1)(2^Prime[n] - 1), {n, 16}] (* _Alonso del Arte_, Dec 12 2012 *)
%o A060286 (PARI) { n=0; forprime (p=1, 542, write("b060286.txt", n++, " ", 2^(p - 1)*(2^p - 1)); ) } \\ _Harry J. Smith_, Jul 03 2009
%Y A060286 Cf. A000040, A000396, A006516.
%K A060286 nonn
%O A060286 1,1
%A A060286 _Jason Earls_, Mar 23 2001