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 A276503 #18 Apr 29 2025 17:32:43
%S A276503 20,26,35,100,130,160,370,400,610,730,793,1000,1570,1843,1930,2500,
%T A276503 2560,2770,2860,3130,3970,4000,4171,4210,4570,5410,5767,6130,6400,
%U A276503 6610,6730,7330,7570,8770,9106,9640,9970,9991,10498,10660,10930,11248
%N A276503 Numbers n such that phi(n) = phi(n+10), with Euler's totient function phi = A000010.
%H A276503 Vincenzo Librandi, <a href="/A276503/b276503.txt">Table of n, a(n) for n = 1..1200</a>
%H A276503 Kevin Ford, <a href="https://arxiv.org/abs/2002.12155">Solutions of phi(n) = phi(n+k) and sigma(n) = sigma(n + k)</a>, arXiv:2002.12155 [math.NT], 2020.
%t A276503 Select[Range[15000], EulerPhi[#] == EulerPhi[# + 10] &]
%t A276503 SequencePosition[EulerPhi[Range[12000]],{x_,_,_,_,_,_,_,_,_,_,x_}][[;;,1]] (* _Harvey P. Dale_, Apr 29 2025 *)
%o A276503 (Magma) [n: n in [1..20000] | EulerPhi(n) eq EulerPhi(n+10)];
%Y A276503 Cf. A000010.
%Y A276503 Cf. numbers n such that phi(n)=phi(n+k): A001274 (k=1), A001494 (k=2), A179186 (k=4), A179187 (k=5), A179188 (k=6), A179189 (k=7), A179202 (k=8), this sequence (k=10), A276504 (k=11), A217139 (k=12).
%K A276503 nonn,easy
%O A276503 1,1
%A A276503 _Vincenzo Librandi_, Sep 08 2016