A103791 - OEIS

%I #4 Mar 31 2012 10:23:47

%S 2,4,8,29,24,78,65,90,449,280,400,124,935,589,1743,325,2001,2863,3150,

%T 2026,5680,5156,4016,10403,22626,2358,19242,14356,19543,7666,20555,

%U 29104,64045,56438,84993,15346,37400,13663,83487,58651,162225,111880

%N Index of the first occurrence of A019565(2n-1) in sequence A103790.

%e A103790(2)=1*2*1-1; => a(1)=2

%e A103790(4)=3*2*2-1; => a(2)=4

%t A019565 = Function[tn, k1 = tn; o = 1; tt = 1; While[k1 > 0, k2 = Mod[k1, 2]; If[k2 == 1, tt = tt*Prime[o]]; k1 = (k1 - k2)/2; o = o + 1]; tt]; Array[fa, {1, 500}]; Do[fa[n] = 0, {n, 1, 500}]; n = 2; npd = Prime[n]; ct = 1; wt = 1; While[wt < 69, cr = (ct + 1)/2; If[fa[cr] == 0, fa[cr] = n; While[fa[wt] > 0, Print[fa[wt]]; wt = wt + 1]]; n = n + 1; npd = Prime[n]; ct = 1; tt = ct; cp = npd + A019565[tt]; While[ ! (PrimeQ[cp]), ct = ct + 1; tt = ct; cp = npd + A019565[tt]]]

%Y Cf. A019565, A103790.

%K nonn

%O 1,1

%A _Lei Zhou_, Feb 16 2005