Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #16 Aug 18 2015 07:59:51
%S 127,2,3,7,5,149,19,41,23899,139,43,761,281,17,53,2551,23,20149,
%T 100720363856036298033578901613089271,31,179,11,13,523,282995646721,
%U 2871347,83,10744429,1031,427773048135533,97,78506876242349,67
%N Euclid-Mullin sequence (A000945) with initial value a(1)=127 instead of a(1)=2.
%H Robert Price, <a href="/A051335/b051335.txt">Table of n, a(n) for n = 1..47</a>
%t a[1]=127; a[n_] := First[ Flatten[ FactorInteger[ 1+Product[ a[ j ], {j, 1, n-1} ] ] ] ]; Array[a, 10]
%o (PARI) spf(n)=my(f=factor(n)[1,1]);f;
%o first(m)={my(v=vector(m)); v[1]=127; for(i=2, m, v[i]=spf(1+prod(j=1, i-1, v[j]))); v;} /* _Anders Hellström_, Aug 18 2015 */
%Y Cf. A000945, A000946, A005265, A005266.
%K easy,nonn
%O 1,1
%A _Labos Elemer_