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 A242963 #21 Sep 08 2022 08:46:08 %S A242963 5,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29, %T A242963 30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52, %U A242963 53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71 %N A242963 Numbers n such that A242962(n) = sigma(n) = A000203(n). %C A242963 A242962(n) = (n*(n+1)/2) mod antisigma(n) = A000217(n) mod A024816(n). %C A242963 Union of number 5 and numbers >= 7. %C A242963 Conjecture: this sequence lists all the positive integers n such that, for some integer k, (sin(k*Pi/n))^2 is irrational. - _Lorenzo Sauras Altuzarra_, Jan 27 2020 %H A242963 Michael De Vlieger, <a href="/A242963/b242963.txt">Table of n, a(n) for n = 1..14995</a> %t A242963 Select[Range[3, 71], DivisorSigma[1, #] == Mod[PolygonalNumber@ #, Total@ Complement[Range@ #, Divisors@ #]] &] (* _Michael De Vlieger_, Jan 28 2020 *) %o A242963 (Magma) [n: n in [3..100000] | ((n*(n+1)div 2) mod (n*(n+1)div 2-SumOfDivisors(n))) eq (SumOfDivisors(n))] %Y A242963 Cf. A000203, A000217, A002961, A024816, A242962, A243117, A243118, A217290, A009005. %K A242963 nonn %O A242963 1,1 %A A242963 _Jaroslav Krizek_, May 29 2014