OFFSET
1,1
COMMENTS
From Antti Karttunen, Nov 15 2014: (Start)
Equally: Odd numbers n for which A246702((n+1)/2) = 2.
Primes in this sequence: 7, 17, 23, 41, 47, 71, 79, ... seem to be A115591.
A249819 gives the composite terms.
(End)
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..105
PROG
(PARI)
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)); }
n = 0; i = 0; while(i < 105, n++; if(isA246717(n), i++; write("b246717.txt", i, " ", n))); \\ From Antti Karttunen, Nov 15 2014
(Scheme, with Antti Karttunen's IntSeq-library)
CROSSREFS
KEYWORD
nonn
AUTHOR
Juri-Stepan Gerasimov, Nov 15 2014
EXTENSIONS
Terms corrected by Antti Karttunen, Nov 15 2014
STATUS
approved