cp's OEIS Frontend

A246717 Numbers of the form 2n - 1 such that A246702(n) = 2.

%I A246717 #29 Nov 16 2014 11:50:09
%S A246717 7,17,23,35,41,47,49,71,77,79,95,97,103,115,137,143,167,175,191,193,
%T A246717 199,209,235,239,245,263,271,289,295,299,311,313,319,335,343,359,367,
%U A246717 371,383,395,401,407,409,413,415,437,449,463,475,479,487,503,515,517,521,529,535,539,551,569,575,581,583,599,607,611,647,649,667,695,707
%N A246717 Numbers of the form 2n - 1 such that A246702(n) = 2.
%C A246717 From _Antti Karttunen_, Nov 15 2014: (Start)
%C A246717 Equally: Odd numbers n for which A246702((n+1)/2) = 2.
%C A246717 Primes in this sequence: 7, 17, 23, 41, 47, 71, 79, ... seem to be A115591.
%C A246717 A249819 gives the composite terms.
%C A246717 (End)
%H A246717 Antti Karttunen, <a href="/A246717/b246717.txt">Table of n, a(n) for n = 1..105</a>
%o A246717 (PARI)
%o A246717 isA246717(n) = { if(!(n%2), return(0), my(u, s=0); u = n^2; for(k=1, u-1, if(!(((2^k)-1)%u), s++;if(s > 2, return(0)))); return(2==s)); }
%o A246717 n = 0; i = 0; while(i < 105, n++; if(isA246717(n), i++; write("b246717.txt", i, " ", n))); \\ From _Antti Karttunen_, Nov 15 2014
%o A246717 (Scheme, with _Antti Karttunen_'s IntSeq-library)
%o A246717 (define A246717 (MATCHING-POS 1 1 (lambda (n) (and (odd? n) (= 2 (A246702 (/ (+ 1 n) 2)))))))
%Y A246717 Cf. A002326, A115591, A249819, A167791, A246702.
%K A246717 nonn
%O A246717 1,1
%A A246717 _Juri-Stepan Gerasimov_, Nov 15 2014
%E A246717 Terms corrected by _Antti Karttunen_, Nov 15 2014