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 A001772 M2145 N0854 #43 Nov 06 2023 14:58:04 %S A001772 2,26,50,54,126,134,246,354,362,950,1310,2498,6926,11826,31734,67850, %T A001772 74726,96150,374114,696438,743322,1044086,1104606,1261478 %N A001772 Numbers k such that 11*2^k - 1 is prime. %D A001772 H. Riesel, "Prime numbers and computer methods for factorization", Progress in Mathematics, Vol. 57, Birkhäuser, Boston, 1985, Chap. 4, see pp. 381-384. %D A001772 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence). %D A001772 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). %H A001772 Wilfrid Keller, <a href="http://www.prothsearch.com/riesel2.html">List of primes k.2^n - 1 for k < 300</a> %H A001772 Kosmaj, <a href="http://www.15k.org/riesellist.html">Riesel list k<300</a>. %H A001772 H. C. Williams and C. R. Zarnke, <a href="http://dx.doi.org/10.1090/S0025-5718-1968-0227095-2">A report on prime numbers of the forms M = (6a+1)*2^(2m-1)-1 and (6a-1)*2^(2m)-1</a>, Math. Comp., 22 (1968), 420-422. %H A001772 <a href="/index/Pri#riesel">Index entries for sequences of n such that k*2^n-1 (or k*2^n+1) is prime</a> %o A001772 (PARI) is(n)=ispseudoprime(11*2^n-1) \\ _Charles R Greathouse IV_, Feb 20 2017 %o A001772 (Python) %o A001772 from sympy import isprime %o A001772 def aupto(lim): return [k for k in range(1, lim+1) if isprime(11*2**k - 1)] %o A001772 print(aupto(2500)) # _Michael S. Branicky_, Feb 26 2021 %Y A001772 Cf. A050525. %Y A001772 Cf. A002261 (11*2^k+1 is prime). %K A001772 hard,nonn,nice,more %O A001772 1,1 %A A001772 _N. J. A. Sloane_ %E A001772 More terms from _Hugo Pfoertner_, Jun 23 2004 %E A001772 More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008