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 A278054 #17 Jul 20 2025 15:03:54 %S A278054 31,127,8191,524287,2147483647,2305843009213693951 %N A278054 Primes p of the form sigma(2^(q+1)) for some prime q. %C A278054 The next term is too large to include (see the table). %C A278054 Corresponding values of primes q are in A278053. %C A278054 Subsequence of Mersenne primes (A000668). %H A278054 Jaroslav Krizek, <a href="/A278054/b278054.txt">Table of n, a(n) for n = 1..7</a> %e A278054 8191 = sigma(2^(q+1)) for prime q = 11. %t A278054 Select[DivisorSigma[1, 2^(# + 1)] & /@ Prime@ Range@ 120, PrimeQ] (* _Michael De Vlieger_, Nov 10 2016 *) %o A278054 (Magma) [SumOfDivisors(2^(n+1)): n in [1..1000] | IsPrime(n) and IsPrime(SumOfDivisors(2^(n+1)))]; %Y A278054 Cf. A000043, A000203, A153798, A278053. %K A278054 nonn %O A278054 1,1 %A A278054 _Jaroslav Krizek_, Nov 09 2016