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 A377951 #12 Nov 16 2024 04:28:25
%S A377951 1,799799,1204280,2460975,3382379,6116175,7050120,8070699,13339424,
%T A377951 20966049,28460600,41265680,41463135,52404624,66108399,68919080,
%U A377951 72946224,81102944,84479680,102971924,106663304,110791736,112375899,115225439,118333215,131115984,132073424
%N A377951 Numbers k such that k | A057643(k) and (k+1) | A057643(k+1).
%C A377951 Numbers k such that k and k+1 are both terms in A377950.
%H A377951 Amiram Eldar, <a href="/A377951/b377951.txt">Table of n, a(n) for n = 1..1000</a>
%t A377951 q[n_] := q[n] = Divisible[LCM @@ (Divisors[n] + 1), n]; Select[Range[4*10^6], q[#] && q[# + 1] &]
%o A377951 (PARI) is1(k) = !(lcm(apply(x->x+1, divisors(k))) % k);
%o A377951 lista(kmax) = {my(q1 = is1(1), q2); for(k = 2, kmax, q2 = is1(k); if(q1 && q2, print1(k-1, ", ")); q1 = q2);}
%Y A377951 Cf. A057643.
%Y A377951 Subsequence of A377950.
%Y A377951 Similar sequences: A355332, A377949, A377953.
%K A377951 nonn
%O A377951 1,2
%A A377951 _Amiram Eldar_, Nov 12 2024