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 A339776 #24 Sep 08 2022 08:46:26
%S A339776 3,252003,293763,770883,1444803,2630883,6543363,8421603,9375843,
%T A339776 18992163,19731363,21883683,22108803,25786083,25989603,32512803,
%U A339776 35259843,48972003,98049603,101566083,132204003,155201763,160224963,162766563,187197123,208455843,291658083
%N A339776 Numbers m such that tau(m) = tau(m + 1) - 1 = tau(m + 2), where tau(k) = the number of divisors of k (A000005).
%C A339776 Corresponding values of tau(a(n)): 2, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, ...
%C A339776 Triplets of [tau(a(n)), tau(a(n) + 1), tau(a(n) + 2)] = [tau(a(n)), tau(a(n)) + 1, tau(a(n))]: [2, 3, 2], [8, 9, 8], [8, 9, 8], [8, 9, 8], [8, 9, 8], [8, 9, 8], [8, 9, 8], [8, 9, 8], [8, 9, 8], ...
%C A339776 a(n) is one less than a perfect square. - _David A. Corneth_, Dec 29 2020
%H A339776 David A. Corneth, <a href="/A339776/b339776.txt">Table of n, a(n) for n = 1..10000</a>
%e A339776 tau(3) = 2, tau(4) = 3, tau(5) = 2.
%t A339776 d1 = 1; d2 = 2; s = {}; Do[d3 = DivisorSigma[0, n]; If[Equal @@ {d1, d2 - 1, d3}, AppendTo[s, n - 2]]; d1 = d2; d2 = d3, {n, 3, 10^7}]; s (* _Amiram Eldar_, Dec 17 2020 *)
%o A339776 (Magma) [m: m in [2..10^6] | #Divisors(m + 1) - 1 eq #Divisors(m) and #Divisors(m + 2) eq #Divisors(m)]
%o A339776 (PARI) isok(m) = my(nb = numdiv(m)); (numdiv(m+2) == nb) && (numdiv(m+1) == nb+1); \\ _Michel Marcus_, Dec 18 2020
%Y A339776 Cf. A000005, A339777.
%Y A339776 Subsequence of A005563.
%Y A339776 Intersection of A062832 and A055927.
%K A339776 nonn
%O A339776 1,1
%A A339776 _Jaroslav Krizek_, Dec 16 2020
%E A339776 More terms from _Amiram Eldar_, Dec 16 2020