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 A067830 #27 Apr 25 2025 04:29:08 %S A067830 5,7,11,17,23,41,47,71,83,101,107,113,131,167,197,227,233,281,311,317, %T A067830 353,383,401,443,461,467,491,503,617,647,677,743,761,773,827,857,863, %U A067830 881,887,911,941,971,1013,1091,1097,1217,1283,1301,1307,1427,1433,1451 %N A067830 Primes p such that sigma(p-4) < p. %C A067830 Except for the first term, terms are primes of the form p+4 with p prime, i.e., the sequence is essentially A031505, A046132. In other words, the solutions to sigma(x) < x + 4 are 1,2,4 and the odd primes. - _Ralf Stephan_, Feb 09 2004 %H A067830 Amiram Eldar, <a href="/A067830/b067830.txt">Table of n, a(n) for n = 1..10000</a> %t A067830 Select[Prime[Range[3, 230]], DivisorSigma[1, #-4] < # &] (* _Amiram Eldar_, Apr 25 2025 *) %o A067830 (PARI) isok(p) = isprime(p) && (p>4) && (sigma(p-4) < p); \\ _Michel Marcus_, Feb 15 2021 %Y A067830 Cf. A000203, A025584, A046022, A067833. %K A067830 nonn,easy %O A067830 1,1 %A A067830 _Benoit Cloitre_, Feb 08 2002 %E A067830 Edited by _Charles R Greathouse IV_, Mar 19 2010