A098831 - OEIS

%I #10 Apr 29 2023 14:01:10

%S 0,1,1,15,51,101,51,1,5,155,1,1051,51,105,5,311,1335,355,105,31,55,51,

%T 105,1031,15,105,55,5,355,115,1001,3115,35,551,331,1,305,51,3305,555,

%U 1111,305,135,1131,1135,1505,51,31,10355,5001,1001,1335,1101,331,305

%N a(n) = A069837(n) - (10^n-1)*2/9.

%C This is a way to compress A069837.

%o (PARI) foo(n) = local(m); if (n < 4, m = q[n + 1], m = q[n%4 + 1] + 10*foo(n\4)); m;

%o print1(0, ", "); q = [0, 1, 3, 5]; for (n = 2, 70, x = (10^n - 1)*2/9; i = 1; found = 0; while (!found, m = foo(i); if (isprime(x + m), found = 1; print1(m, ", "), i += 2)));

%Y Cf. A069837.

%K base,easy,nonn,less

%O 1,4

%A _David Wasserman_, Nov 02 2004