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 A260071 #33 Jul 01 2025 21:39:58 %S A260071 2,3,23,970388922263,991817878343,1677028870823 %N A260071 Primes p such that sigma(p) = sigma(p+1) - sigma(p-1). %C A260071 Primes from A076530 (numbers n such that sigma(n) = sigma(n+1) - sigma(n-1)). %C A260071 Also primes from sequence A260420 (numbers n such that sigma(n+1) - sigma(n-1) = n+1). %C A260071 If a number from A246852(n) + 1 is a prime p, then p is in the sequence. %C A260071 If a(7) exists, it must be bigger than 10^13. %e A260071 23 is in the sequence because sigma(24) - sigma(22) = 60 - 36 = 24 = sigma(23). %o A260071 (Magma) [n: n in [1..1000000] | IsPrime(n) and SumOfDivisors(n) eq ((SumOfDivisors(n+1)) - (SumOfDivisors(n-1)))]; %o A260071 (Magma) [n: n in [A076530(n)] | IsPrime(n)]; %o A260071 (PARI) is_ok(index)=my(p=prime(index)); p+1==sigma(p+1)-sigma(p-1); %o A260071 main(size)=my(v=vector(size),index=1);for(i=1,size,while(!is_ok(index),index++);v[i]=prime(index);index++); v \\ _Anders Hellström_, Jul 14 2015 %o A260071 (PARI) has(p)=p+1==sigma(p+1)-sigma(p-1) %o A260071 select(has, primes(1000)) \\ _Charles R Greathouse IV_, Jul 22 2015 %Y A260071 Cf. A000203, A076530, A246852. %K A260071 nonn,more,hard %O A260071 1,1 %A A260071 _Jaroslav Krizek_, Jul 14 2015