cp's OEIS Frontend

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.

A075033 Numbers n such that tau(n) <= tau(n+1) <= tau(n+2) <= tau(n+3) where tau(n) = number of divisors of n.

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%I A075033 #23 Jul 10 2020 14:09:17
%S A075033 1,13,25,33,37,61,73,85,93,97,121,133,141,145,157,187,193,201,205,213,
%T A075033 217,229,241,242,243,253,277,283,301,361,373,393,397,421,427,445,453,
%U A075033 457,481,537,541,547,603,613,633,661,662,663,697,723,733,745,757,781
%N A075033 Numbers n such that tau(n) <= tau(n+1) <= tau(n+2) <= tau(n+3) where tau(n) = number of divisors of n.
%H A075033 Karl V. Keller, Jr., <a href="/A075033/b075033.txt">Table of n, a(n) for n = 1..10000</a>
%t A075033 With[{s = Partition[Differences@ Array[DivisorSigma[0, #] &, 800], 3, 1]}, Position[s, _?(AllTrue[#, # >= 0 &] &), {1}, Heads -> False][[All, 1]]] (* _Michael De Vlieger_, Jun 28 2020 *)
%o A075033 (Python)
%o A075033 from sympy import divisor_count as tau
%o A075033 [n for n in range(1, 801) if tau(n) <= tau(n+1) <= tau(n+2) <= tau(n+3)] # _Karl V. Keller, Jr._, Jul 10 2020
%Y A075033 Cf. A000005, A075032, A075034, A075035.
%K A075033 nonn
%O A075033 1,2
%A A075033 _Amarnath Murthy_, Sep 02 2002
%E A075033 Added missing term and a(11)-a(54) from _Donovan Johnson_, Jun 15 2009