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 A091815 #21 Aug 27 2024 16:58:35
%S A091815 3,4,5,6,7,9,11,13,15,16,17,22,61,69,73,97,120,125,138,141,158,180,
%T A091815 183,220,224,317,370,457,517,546,573,648,678,692,699,804,848,1182,
%U A091815 1213,1225,1300,1866,2093,2344,2411,2837,3421,4888,5685,6530,6788,7009,7076,7465,7674,7757
%N A091815 Numbers m such that the numerator of Sum_{i=1..m} (i-1)/i is prime.
%H A091815 Michael S. Branicky, <a href="/A091815/b091815.txt">Table of n, a(n) for n = 1..93</a>
%t A091815 Select[Range[3000],PrimeQ[Numerator[Sum[(i-1)/i,{i,#}]]]&] (* _Harvey P. Dale_, Jul 13 2011 *)
%t A091815 Position[Accumulate[Table[(k-1)/k,{k,3000}]],_?(PrimeQ[Numerator[#]]&)]// Flatten (* _Harvey P. Dale_, Jun 06 2021 *)
%o A091815 (PARI) ss(n)=sum(i=1,n,(i-1)/i); for (i=1,1200,if(isprime(numerator(ss(i))),print1(i,".")))
%Y A091815 Cf. A091816, A187487.
%K A091815 hard,nonn
%O A091815 1,1
%A A091815 Mohammed Bouayoun (bouyao(AT)wanadoo.fr), Mar 07 2004
%E A091815 a(39)-a(46) from _Harvey P. Dale_, Jul 13 2011
%E A091815 a(47) and beyond from _Michael S. Branicky_, Aug 26 2024