A080829 Primes that terminate at 20,10,5 in the 3x-1 problem: Repeat, if x is even divide by 2 else multiply by 3 and subtract 1, until 5 is reached.

5, 7, 13, 19, 47, 89, 107, 139, 149, 167, 181, 191, 199, 223, 241, 251, 271, 281, 317, 353, 383, 397, 401, 421, 431, 499, 503, 509, 541, 571, 593, 601, 607, 631, 643, 709, 797, 809, 811, 839, 859, 887, 941, 947, 997

Offset

1,1

Links

Table of n, a(n) for n=1..45.

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 == 5, print1(x" ")) ) }

Crossrefs

Sequence in context: A189557 A045444 A129782 * A224789 A078884 A314328

Adjacent sequences: A080826 A080827 A080828 * A080830 A080831 A080832

Keyword

easy,nonn

Author

Cino Hilliard, Mar 27 2003

Status

approved