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A260724 a(1) = 2; for n > 1 if n mod 3=0 a(n) = gpf(1 + Product_{m modulo 3=2,m<n} a(m)), if n modulo 3=1 a(n) = gpf(1 + Product_{m modulo 3=0,m<n} a(m)), if n modulo 3=2 a(n) = gpf(1 + Product_{m modulo 3=1,m<n} a(m)). 1
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

PROG

(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; }

CROSSREFS

Cf. A258581

Sequence in context: A118007 A195401 A158747 * A256581 A122697 A129022

Adjacent sequences:  A260721 A260722 A260723 * A260725 A260726 A260727

KEYWORD

nonn

AUTHOR

Anders Hellström, Jul 30 2015

STATUS

approved

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Last modified October 14 00:25 EDT 2019. Contains 327991 sequences. (Running on oeis4.)