A328225 - OEIS

A328225

a(1) = 1, a(n) = a(n-1) - prime(prime(n)) - prime(n-1) if this produces a positive integer not yet in the sequence, otherwise a(n) = a(n-1) + prime(prime(n)) - prime(n-1).

%I #27 Oct 31 2019 01:56:42

%S 1,4,12,24,48,78,6,56,120,206,50,176,318,86,254,448,118,342,612,192,

%T 488,14,366,744,146,596,1058,368,860,134,730,1342,438,1098,100,828,

%U 1596,472,1300,102,992,1900,566,1546,152,1172,2270,650,1860,186,1428,2694,932,2288,416

%N a(1) = 1, a(n) = a(n-1) - prime(prime(n)) - prime(n-1) if this produces a positive integer not yet in the sequence, otherwise a(n) = a(n-1) + prime(prime(n)) - prime(n-1).

%H Connor O'Higgins, <a href="/A328225/b328225.txt">Table of n, a(n) for n = 1..10000</a>

%H Connor O'Higgins, <a href="/A328225/a328225_2.txt">Matlab code for a(n) for n = 1..10000</a>

%K nonn,look

%O 1,2

%A _Connor O'Higgins_, Oct 08 2019