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 A199970 #12 Jan 23 2025 10:25:05 %S A199970 0,3,4,6,12,0,60,420,840,0,2520,0,27720,0,0,360360,720720,0,12252240, %T A199970 0,0,0,232792560,0,5354228880,0,26771144400,0,80313433200,0, %U A199970 2329089562800,72201776446800,0,0,0,0,144403552893600,0,0,0,5342931457063200,0,219060189739591200 %N A199970 a(n) = the smallest number m with the smallest non-divisor n such that 1<n<m, or 0 if no such m exists. %F A199970 a(n) > 0 for prime powers n = p^k (p prime, k >= 1) else 0. %F A199970 a(n) = A003418(n-1) for n = p^k > 3 (p prime, k >= 1). - _Amiram Eldar_, Aug 06 2024 %e A199970 a(7) = 60 because 60 is the smallest number such that numbers k < 7 divides 60 but number 7 is not divisor of 60. %t A199970 a[n_] := If[PrimePowerQ[n], If[n <= 3, n+1, LCM @@ Range[n-1]], 0]; Array[a, 50] (* _Amiram Eldar_, Aug 06 2024 *) %Y A199970 Cf. A003418, A199968, A199969. %K A199970 nonn %O A199970 1,2 %A A199970 _Jaroslav Krizek_, Nov 26 2011 %E A199970 More terms from _Amiram Eldar_, Aug 06 2024