A080830 Primes that terminate at 68,34,17 in the 3x-1 problem: Repeat, if x is even divide by 2 else multiply by 3 and subtract 1, until 17 is reached.

17, 23, 31, 37, 41, 61, 67, 73, 83, 109, 131, 163, 179, 197, 229, 233, 239, 257, 263, 277, 293, 311, 313, 331, 337, 349, 389, 439, 443, 449, 457, 467, 491, 521, 523, 557, 577, 587, 599, 641, 659, 661, 673, 677, 701, 739, 743, 757, 761, 769, 773, 787, 829, 877

Offset

1,1

Links

Table of n, a(n) for n=1..54.

Prog

(PARI) px3nm1(n, p) = { forprime(x=2, n, p1 = x; while(p1>1, if(p1%2==0, p1/=2, p1 = p1*p-1; ); if(p1 == 5 || p1==17, break); ); if(p1 == 17, print1(x" ")) ) }

Crossrefs

Sequence in context: A330600 A217044 A145484 * A165566 A072184 A377172

Adjacent sequences: A080827 A080828 A080829 * A080831 A080832 A080833

Keyword

easy,nonn

Author

Cino Hilliard, Mar 27 2003

Status

approved