OFFSET
1,1
LINKS
Tyler Busby, Table of n, a(n) for n = 1..44
MATHEMATICA
a[1]=257; a[n_] := First[ Flatten[ FactorInteger[ 1+Product[ a[ j ], {j, 1, n-1} ] ] ] ]; Array[a, 10]
PROG
(PARI) spf(n)=my(f=factor(n)[1, 1]); f \\ A020639
first(m)=my(v=vector(m)); v[1]=257; for(i=2, m, v[i]=spf(1+prod(j=1, i-1, v[j]))); v \\ Anders Hellström, Dec 07 2015
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
a(22)-a(27) from Robert Price, Jul 09 2015
a(28)-a(40) from Tyler Busby, Oct 12 2023
STATUS
approved