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 A278053 #20 Jul 20 2025 15:03:47 %S A278053 3,5,11,17,29,59,1277,4421,110501,132047,20996009,24036581 %N A278053 Primes p such that sigma(2^(p+1)) is prime. %C A278053 Primes in A153798 = A000043 - 2 where A000043 = Mersenne exponents. %C A278053 Corresponding values of primes q are in A278054. %C A278053 See A000043 (Mersenne exponents) - numbers n such that sigma(2^(n-1)) is a prime. %e A278053 Prime 11 is in the sequence because sigma(2^(11+1)) = sigma(4096) = 8191 (prime). %t A278053 (* set the terms in A000043 = lst *) Select[lst, PrimeQ[# - 2] &] (* _Robert G. Wilson v_, Nov 09 2016 *) %o A278053 (Magma) [n: n in [1..10000] | IsPrime(n) and IsPrime(SumOfDivisors(2^(n+1)))]; %o A278053 (PARI) is(n)=isprime(n) && isprime(n+2) && isprime(2^(n+2)-1) \\ _Charles R Greathouse IV_, Nov 09 2016 %Y A278053 Cf. A000043, A000203, A153798, A278054. %K A278053 hard,nonn,more %O A278053 1,1 %A A278053 _Jaroslav Krizek_, Nov 09 2016