A260724 a(1) = 2; for n > 1 if n mod 3=0 a(n) = gpf(1 + Product_{m modulo 3=2,m

2, 3, 2, 7, 5, 2, 31, 3, 109, 13, 97, 83, 8731, 461, 3078769, 574933, 206179, 510583, 5153873111, 1900169, 372828179, 4032506435771041, 3445362972116384083, 49898596950715368948711529590337583, 54176564592185030069557382121821

Offset: 1

Author

Anders Hellström, Jul 30 2015

Keywords

• nonn

Links

• Anders Hellström, Table of n, a(n) for n = 1..27

Crossrefs

Cf. A258581

Programs

PARI

gpf(n)=my(v=factor(n)[, 1]); v[#v];
first(m)={my(v=vector(m),one=2,two=2,three=1);v[1]=2;for(i=2, m,if(i%3===0,v[i]=gpf(three+1);two*=v[i],if(i%3===1,v[i]=gpf(one+1);three*=v[i],v[i]=gpf(two+1);one*=v[i])));v;}