cp's OEIS Frontend

A340077 Odd numbers k for which k-1 is a multiple of A053575(k) [the odd part of phi(k)].

%I A340077 #8 Dec 30 2020 19:59:52
%S A340077 1,3,5,7,11,13,15,17,19,23,29,31,37,41,43,47,51,53,59,61,67,71,73,79,
%T A340077 83,85,89,91,97,101,103,107,109,113,127,131,137,139,149,151,157,163,
%U A340077 167,173,179,181,191,193,197,199,211,223,227,229,233,239,241,251,255,257,263,269,271,277,281,283,293,307,311,313
%N A340077 Odd numbers k for which k-1 is a multiple of A053575(k) [the odd part of phi(k)].
%C A340077 Sequence A003961(A340076(i)), i = 1.., sorted into ascending order. In other words, this sequence consists of such odd numbers k that A064989(k) is in A340076.
%H A340077 Antti Karttunen, <a href="/A340077/b340077.txt">Table of n, a(n) for n = 1..10000</a>
%o A340077 (PARI)
%o A340077 A000265(n) = (n>>valuation(n, 2));
%o A340077 isA340077(n) = ((n%2)&&!((n-1)%A000265(eulerphi(n))));
%o A340077 (PARI)
%o A340077 A064989(n) = { my(f=factor(n)); if((n>1 && f[1,1]==2), f[1,2] = 0); for (i=1, #f~, f[i,1] = precprime(f[i,1]-1)); factorback(f) };
%o A340077 isA340077(n) = ((n%2)&&(1==A340075(A064989(n)))); \\ Needs also code from A340075.
%Y A340077 Cf. A064989, A340075, A340076.
%Y A340077 Subsequence of A339879.
%Y A340077 Subsequences: A065091, A339880 (composite terms), A339869, A339870 (and their further subsequences).
%K A340077 nonn
%O A340077 1,2
%A A340077 _Antti Karttunen_, Dec 29 2020