A119691 - OEIS

A119691

Numbers n which do not divide any 3^x-2, even though each prime factor of n does divide some 3^x-2.

35, 85, 133, 145, 155, 175, 203, 217, 245, 265, 301, 323, 371, 395, 425, 445, 493, 505, 553, 565, 589, 595, 635, 665, 679, 685, 707, 725, 731, 775, 805, 817, 875, 889, 899, 901, 931, 973, 985, 995, 1015, 1043, 1085, 1115, 1141, 1165, 1205, 1211, 1225

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

EXAMPLE

35 is here because 5 divides 3^3-2 and 7 divides 3^2-2, but 35 divides no 3^x-2.

PROG

(PARI) isA123239(n)=if(!isprime(n), return(0)); if(n<5, return(1)); my(m=Mod(3, n)); while(m!=1, m*=3; if(m==2, return(0))); 1

is(n)=if(n<9||isprime(n), return(0)); my(f=factor(n)[, 1]); for(i=1, #f, if(isA123239(f[i]), return(0))); my(m=Mod(3, n)); while(m!=1, m*=3; if(m==2, return(0))); 1 \\ Charles R Greathouse IV, Jul 07 2013

CROSSREFS

Cf. A123239, A131960.

Sequence in context: A044173 A044554 A156126 * A220007 A115393 A086337

Adjacent sequences: A119688 A119689 A119690 * A119692 A119693 A119694

KEYWORD

nonn

AUTHOR

A.K. Devaraj, Jul 23 2007

EXTENSIONS

Edited by Don Reble, Aug 04 2007

STATUS

approved