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.

A372896 Squarefree terms of A372894 whose prime factors are neither elite (A102742) nor anti-elite (A128852).

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%I A372896 #9 May 22 2024 15:12:27
%S A372896 1,341,671,1891,2117,3277,4033,5461,8249,12557,13021,14531,19171,
%T A372896 24811,31609,32777,33437,40951,46139,48929,49981,50737,73279,80581,
%U A372896 84169,100253,116143,130289,135923,136271,149437,175577,179783,194417,252361,272491,342151,343027,376169,390641
%N A372896 Squarefree terms of A372894 whose prime factors are neither elite (A102742) nor anti-elite (A128852).
%C A372896 By construction, A372894 is the disjoint union of the two following sets of numbers: (a) products of a square, some distinct anti-elite primes, an even number of elite-primes and a term here; (b) products of a square, some distinct anti-elite primes, an odd number of elite-primes and a term in A372895.
%o A372896 (PARI) isA372896(n) = {
%o A372896 if(n%2 && issquarefree(n) && isA372894(n), if(n==1, return(1)); my(f = factor(n)~[1,]); \\ See A372894 for its program
%o A372896 for(i=1, #f, my(p=f[i], d = znorder(Mod(2, p)), StartPoint = valuation(d, 2), LengthTest = znorder(Mod(2, d >> StartPoint)), flag = 0); \\ To check if p = f[i] is an elite prime or an anti-elite prime, it suffices to check (2^2^i + 1) modulo p for StartPoint <= i <= StartPoint + LengthTest - 1; see A129802 or A372894
%o A372896 for(j = StartPoint+1, StartPoint + LengthTest - 1, if(issquare(Mod(2, p)^2^j + 1) != issquare(Mod(2, p)^2^StartPoint + 1), flag = 1; break())); if(flag == 0, return(0))); 1, 0)
%o A372896 }
%Y A372896 Cf. A372894, A102742, A128852, A129802, A372895.
%K A372896 nonn
%O A372896 1,2
%A A372896 _Jianing Song_, May 15 2024