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 A246914 #38 Sep 08 2022 08:46:09 %S A246914 7,103,1487,9679,73727,603679 %N A246914 Primes p such that sigma(2p+1) = 3*(p+1). %C A246914 Primes p such that sigma(p+sigma(p)) = 3*sigma(p). Subsequence of A246910. %C A246914 The next term, if it exists, must be greater than 10^9. %C A246914 Conjecture: Also primes p such that sigma(2p+1) mod p = 3. - _Jaroslav Krizek_, Sep 28 2014 %C A246914 No other terms up to 10^11. - _Michel Marcus_, Feb 21 2020 %e A246914 Prime 7 is in sequence because sigma(2*7 + 1) = sigma(15) = 24 = 3*(7+1). %p A246914 with(numtheory): A246914:=n->`if`(isprime(n) and sigma(2*n+1) = 3*(n+1), n, NULL): seq(A246914(n), n=1..10^5); # _Wesley Ivan Hurt_, Oct 01 2014 %t A246914 Select[Prime[Range[1500]], DivisorSigma[1, 2# + 1] == 3# + 3 &] (* _Alonso del Arte_, Sep 07 2014 *) %o A246914 (Magma) [n:n in[1..10^7] | SumOfDivisors(n+SumOfDivisors(n))eq 3*SumOfDivisors(n) and IsPrime(n)] %o A246914 (PARI) %o A246914 for(n=1,10^6,p=prime(n);if(sigma(p+sigma(p))==3*sigma(p),print1(p,", "))) \\ _Derek Orr_, Sep 07 2014 %o A246914 (PARI) forprime(p=2,10^7,if(sigma(2*p+1)==3*(p+1),print1(p,","))) \\ _Edward Jiang_, Sep 07 2014 %Y A246914 Cf. A000203, A246456, A246910. %K A246914 nonn,more %O A246914 1,1 %A A246914 _Jaroslav Krizek_, Sep 07 2014