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 A275156 #18 Jan 25 2024 05:22:27
%S A275156 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,20,21,24,25,26,27,32,33,34,
%T A275156 35,39,44,48,49,50,51,54,55,63,64,65,77,80,84,90,98,99,104,119,120,
%U A275156 125,135,143,153,168,169,175,195,220,224,242,255,272,288,324,350,351,363,374,384,440,441,539,560,594,624,675,714,728,832,935,1000,1088,1155,1224,1274,1700,1715,2057,2079,2400,2430,2499,2600,3024,4095,4224,4374,4913,5831,6655,9800,10647,12375,14399,28560,31212,37179,123200,194480,336140
%N A275156 The 108 numbers n such that n(n+1) is 17-smooth.
%C A275156 This is the 7th row of the table A138180.
%D A275156 See A002071.
%t A275156 pMax = 17; smoothMax = 10^12; smoothNumbers[p_?PrimeQ, max_] := Module[{a, aa, k, pp, iter}, k = PrimePi[p]; aa = Array[a, k]; pp = Prime[Range[k]]; iter = Table[{a[j], 0, PowerExpand@Log[pp[[j]], max/Times @@ (Take[pp, j - 1]^Take[aa, j - 1])]}, {j, 1, k}]; Table[Times @@ (pp^aa), Sequence @@ iter // Evaluate] // Flatten // Sort]; Select[(Sqrt[1 + 4*smoothNumbers[pMax, smoothMax]] - 1)/2, IntegerQ]
%o A275156 (PARI) is(n)=my(t=510510); n*=n+1; while((t=gcd(n,t))>1, n/=t); n==1 \\ _Charles R Greathouse IV_, Nov 13 2016
%Y A275156 Cf. A002071, A145604, A138180, A145605, A002072, A085152, A085153, A252493, A252492.
%K A275156 nonn,fini,full
%O A275156 1,2
%A A275156 _Jean-François Alcover_, Nov 13 2016