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 A101994 #9 May 13 2024 02:14:25 %S A101994 45,13410,15855,31710,31785,63570,74025,85230,151830,202635,267300, %T A101994 280665,399675,405405,455250,466560,478170,480240,511335,534600, %U A101994 539475,561330,569520,589305,666945,716460,743160,748215,766785,799350,860835 %N A101994 Numbers k such that 4*k-1, 8*k-1, 16*k-1, 32*k-1 and 64*k-1 are all primes. %H A101994 Amiram Eldar, <a href="/A101994/b101994.txt">Table of n, a(n) for n = 1..10000</a> %e A101994 4*45-1 = 179, 8*45-1 = 359, 16*45-1 = 719, 32*45-1 = 1439 and 64*45-1 = 2879 are primes, so 45 is a term. %t A101994 Select[Range[10^6], And @@ PrimeQ[2^Range[2, 6]*# - 1] &] (* _Amiram Eldar_, May 13 2024 *) %o A101994 (PARI) is(k) = isprime(4*k-1) && isprime(8*k-1) && isprime(16*k-1) && isprime(32*k-1) && isprime(64*k-1); \\ _Amiram Eldar_, May 13 2024 %Y A101994 Cf. A002515, A101995, A101996, A101997, A101998, A101999. %Y A101994 Subsequence of A005099, A005122, A101790 and A101794. %K A101994 easy,nonn %O A101994 1,1 %A A101994 Douglas Stones (dssto1(AT)student.monash.edu.au), Dec 23 2004