A258581 - OEIS

A258581

a(1) = 2; for n > 1 if n is even a(n) = gpf(1 + Product_{odd m,m<n}a(m)), while if n is odd a(n) = gpf(1 + Product_{even m,m<n}a(m)).

2, 3, 2, 5, 2, 3, 23, 37, 17, 149, 761, 50647, 4799, 411527, 18871308021859, 10312625105789, 17838863896549, 57892815889963361050999657943, 2252973546284243766517, 1849093263449444009859625443689931115519009693

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OFFSET

1,1

LINKS

Table of n, a(n) for n=1..20.

Anders Hellström, Sage program

Anders Hellström, Mercury program

PROG

(PARI) gpf(n)=my(v=factor(n)[, 1]); v[#v];

main(size)=my(v=vector(size), i, odd=2, even=1); v[1]=2; for(i=2, size, if(i%2==0, v[i]=gpf(odd+1); even*=v[i], v[i]=gpf(even+1); odd*=v[i])); v;

CROSSREFS

Cf. A000946, A005266.

Sequence in context: A000705 A073751 A319431 * A108501 A166226 A263978

Adjacent sequences: A258578 A258579 A258580 * A258582 A258583 A258584

KEYWORD

nonn

AUTHOR

Anders Hellström, Jul 15 2015

STATUS

approved