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A222948
Numbers k such that 3*k+1 divides 3^k+1.
1
0, 1, 9, 3825, 6561, 102465, 188505, 190905, 1001385, 1556985, 3427137, 5153577, 5270625, 5347881, 13658225, 14178969, 20867625, 23828049, 27511185, 29400657, 48533625, 80817009, 83406609, 89556105, 108464265, 123395265, 127558881, 130747689, 133861905
OFFSET
1,3
COMMENTS
This is to 3 as A224486 is to 2
Displayed terms complete up to 200*10^6. - Joerg Arndt, Apr 08 2013
LINKS
Joerg Arndt, Table of n, a(n) for n = 1..64 (all terms <= 10^9)
FORMULA
{n such that (1+A000244(n))/A016777(n) is an integer}.
EXAMPLE
0 is a term because (3^0+1)/(3*0+1) = 2.
1 is a term because (3^1+1)/(3*1+1) = 1.
9 is a term because (3^9+1)/(3*9+1) = 703.
PROG
(PARI) for(n=0, 10^9, if((3^n+1)%(3*n+1)==0, print1(n, ", "))); /* Joerg Arndt, Apr 08 2013 */
/* the following program is significantly faster; it gives terms >=1: */
(PARI) for(n=0, 10^12, my(m=3*n+1); if( Mod(3, m)^n==Mod(-1, m), print1(n, ", ") ) ); /* Joerg Arndt, Apr 08 2013 */
CROSSREFS
Cf. A224486 (k such that 2*k+1 divides 2^k+1).
Sequence in context: A238120 A229151 A162013 * A281876 A046896 A036516
KEYWORD
nonn,changed
AUTHOR
Jonathan Vos Post, Apr 07 2013
EXTENSIONS
Terms > 9 from Joerg Arndt, Apr 08 2013
STATUS
approved