This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A236388 #13 Jul 23 2025 09:15:14 %S A236388 3,2,7,5,19,11,31,17,37,13,23,79,41,29,97,53,43,139,47,71,157,83,59, %T A236388 199,67,211,229,61,131,271,137,307,103,107,109,331,337,113,173,367, %U A236388 379,127,197,439,227,163,499,101,73,263,547,281,577,293,601,607 %N A236388 Primes in order of first appearance among the prime factors of p+1 where p is a prime. %C A236388 The first p+1 (p prime) is 2+1=3, so 3 is the first term of the sequence. The next is 3+1=4=2*2, and the prime 2 appears next, so it is the second term of the sequence. The next p+1 = 5+1 = 6 gives no new prime factor; neither do 7+1 = 8 and 11+1 = 12. 13+1 = 14 = 2*7 gives the new prime factor 7, so 7 is the third term of the sequence. %C A236388 If "p+1" is changed to "p-1" we get A112037. - _N. J. A. Sloane_, Jan 24 2014 %H A236388 Alois P. Heinz, <a href="/A236388/b236388.txt">Table of n, a(n) for n = 1..10000</a> %t A236388 DeleteDuplicates[ First /@ Flatten[FactorInteger[1 + Prime@Range@200], 1]] (* _Giovanni Resta_, Jan 24 2014 *) %Y A236388 Cf. A112037. %K A236388 nonn,easy %O A236388 1,1 %A A236388 _Joseph L. Pe_, Jan 24 2014