login

Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.

a(n) is the smallest prime p > a(n-1) such that p - a(n-1) is an (n-1)-almost prime; a(1) = 2.
0

%I #38 Jul 31 2021 04:36:35

%S 2,5,11,19,43,151,311,439,823,2551,6007,12919,23159,35447,92791,

%T 203383,535159,731767,1124983,5253751,6302327,16919159,32647799,

%U 103426679,160049783,285878903,386542199,1066019447,1468672631,2676632183,5092551287,16366840439,32472967799

%N a(n) is the smallest prime p > a(n-1) such that p - a(n-1) is an (n-1)-almost prime; a(1) = 2.

%e a(2) - a(1) = 5 - 2 = 3, which is prime (a "1-almost prime");

%e a(3) - a(2) = 11 - 5 = 6 = 2*3, which is semiprime (2-almost prime).

%K nonn

%O 1,1

%A _Zak Seidov_, Nov 16 2016

%E a(32)-a(33) from _Jinyuan Wang_, Jul 31 2021