A222948 Numbers n such that 3n+1 divides 3^n+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

a(1) = 0 because (3^0+1)/(3*0+1) = 2.
a(2) = 1 because (3^1+1)/(3*1+1) = 1.
a(3) = 9 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 (n such that 2n+1 divides 2^n+1).

Sequence in context: A238120 A229151 A162013 * A281876 A046896 A036516

Adjacent sequences: A222945 A222946 A222947 * A222949 A222950 A222951

Keyword

nonn

Author

Jonathan Vos Post, Apr 07 2013

Extensions

Terms > 9 from Joerg Arndt, Apr 08 2013

Status

approved