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 A380662 #6 Mar 04 2025 23:25:19
%S A380662 2,3,6,11,16,25,30,34,35,39,44,49,58,68,73,79,82,84,87,89,92,103,106,
%T A380662 111,113,121,123,126,131,146,154,155,159,160,170,183,188,193,202,207,
%U A380662 212,217,219,224,226,228,236,248,251,266,271,279,280,284,289,295
%N A380662 Numbers m such that Sum_{k>=0} floor(m/5^k) is prime.
%e A380662 floor(16/1) + floor(16/5) = 19, so 16 is in the sequence.
%t A380662 f[n_] := Sum[Floor[(n-1)/5^k], {k, 0, Floor[Log[5, n]]}] (* A191610 *)
%t A380662 Select[Range[400], PrimeQ[f[#]] &]
%Y A380662 Cf. A191610, A381239.
%K A380662 nonn
%O A380662 1,1
%A A380662 _Clark Kimberling_, Feb 19 2025