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 A072530 #8 Aug 20 2025 17:42:46
%S A072530 0,0,0,0,1,0,1,2,1,1,1,2,2,2,1,3,3,3,2,3,1,3,3,5,2,4,2,4,3,4,3,4,4,3,
%T A072530 2,6,4,5,2,6,4,6,3,6,4,5,5,7,4,6,4,5,4,8,3,5,4,7,5,9,3,7,5,8,5,7,3,8,
%U A072530 4,8,5,10,6,7,5,8,4,9,6,9,7,8,4,10,5,7,6,8,7,12,5,8,8,8,5,12,6,10,5,10,5
%N A072530 Number of primes p < n such that n divided by p leaves a prime remainder.
%C A072530 Is there any n > 6 such that a(n) = 0?
%e A072530 a(17) = 3: there are 3 primes viz. 3, 5 and 7 which leave prime remainders on dividing 17.
%t A072530 Table[Count[PrimeQ[Table[Mod[w, Prime[j]], {j, 1, PrimePi[w]}]], True], {w, 1, 256}]
%Y A072530 Cf. A072531.
%K A072530 nonn
%O A072530 1,8
%A A072530 _Amarnath Murthy_, Aug 01 2002
%E A072530 More terms from _Labos Elemer_, Aug 02 2002
%E A072530 Name clarified by _Felix Huber_, Aug 20 2025